[Nova Launcher] Abhinav1997:
Icon Pack:

Make sure the icon pack you want to use, you have with you. But before adding them, some details-

Density Icon Size(px)

ldpi 36x36
mdpi 48x48
hdpi 72x72
xhdpi 96x96
xxhdpi 144x144
xxxhdpi 192x192

Ok now put the required icons with proper scaling into drawable-hdpi folder(well you could put in any drawable folder) and name it accordingly. I know many guides tell us to have the names of icons as package name but I didn't really needed to do them so you could do name them according to you but make sure to have name in lower-cases.

Now go to /res/xml and open appfilter.xml

You can find the activity name for browser. The sample name used for any activity is-

<item component="ComponentInfo{com.package.name/com.package.name.ActivityName}" drawable="icon_name"/>

You can find many more here- http://activities.droidicon.com/

Now go to iconpack.xml in /res/values and add the names icons in item tags inside the string array for icon pack.

Next go back to appfilter.xml.

You can see lines like:

<iconback img1="iconback" />
<iconmask img1="iconmask" />
<iconupon img1="iconupon" />
<scale factor="1.1" />

This gives uniformity, scaling and similar look to all your icons, even those not included in your pack so that all of them looks kind of similar.

Wallpapers:

Add all the wallpapers you want to add in drawable-nodpi folder. Also scale them to a small size, check sample theme for reference. Also in the smaller wallpaper, name it same to the original wallpaper but after that put "_small". E.g. the small thumbnail for a wallpaper named as x.png would be x_small.png.

Next open res/values/wallpapers.xml and according to the given list add all the list of wallpapers you have added. Also set a default wallpaper by writing name under

<string name="default_wallpaper">WRITE WALLPAPER NAME HERE</string>

This will be enough for setting wallpaper.

Fonts:

This is the simplest part. Just collect all the fonts you want to add and put them in /assets folder.

Changing your general information:

Now open /res/values/strings.xml. Here change everything according to your wish under the "Basic theme Information" comment.

Changing previews and feature graphinc:

Now apex launcher shows a feature graphic of your theme. So choose a good feature image of proper size and replace the one in drawable-hdpi with your new one. Also add some previews(upto 5) which all the people can see before installing. Just give them any name. I prefer preview1,preview2,etc.

Next open res/values/strings.xml and change the feature name to whatever the name of your feature image is. Leave as it is if you haven't change the name.

Similarly change names of preview and add some more in the same manner if you want but not more than 5.

This part of the tutorial can be left here and you could straight-away jump to the 3rd post. But if you are interested to make even better changes, read further on

Colors:

Now as you can see many of the colours, like some background colors or outlines are not the way you want. You can change those colours. Go to res/values/colors.xml. Here you can change all the colours you want. Here's a list of hexadecimal codes of colours-

<?xml version="1.0" encoding="utf-8"?>
<resources>
<color name="White">#FFFFFF</color>
<color name="Ivory">#FFFFF0</color>
<color name="LightYellow">#FFFFE0</color>
<color name="Yellow">#FFFF00</color>
<color name="Snow">#FFFAFA</color>
<color name="FloralWhite">#FFFAF0</color>
<color name="LemonChiffon">#FFFACD</color>
<color name="Cornsilk">#FFF8DC</color>
<color name="Seashell">#FFF5EE</color>
<color name="LavenderBlush">#FFF0F5</color>
<color name="PapayaWhip">#FFEFD5</color>
<color name="BlanchedAlmond">#FFEBCD</color>
<color name="MistyRose">#FFE4E1</color>
<color name="Bisque">#FFE4C4</color>
<color name="Moccasin">#FFE4B5</color>
<color name="NavajoWhite">#FFDEAD</color>
<color name="PeachPuff">#FFDAB9</color>
<color name="Gold">#FFD700</color>
<color name="Pink">#FFC0CB</color>
<color name="LightPink">#FFB6C1</color>
<color name="Orange">#FFA500</color>
<color name="LightSalmon">#FFA07A</color>
<color name="DarkOrange">#FF8C00</color>
<color name="Coral">#FF7F50</color>
<color name="HotPink">#FF69B4</color>
<color name="Tomato">#FF6347</color>
<color name="OrangeRed">#FF4500</color>
<color name="DeepPink">#FF1493</color>
<color name="Fuchsia">#FF00FF</color>
<color name="Magenta">#FF00FF</color>
<color name="Red">#FF0000</color>
<color name="OldLace">#FDF5E6</color>
<color name="LightGoldenrodYellow">#FAFAD2</color>
<color name="Linen">#FAF0E6</color>
<color name="AntiqueWhite">#FAEBD7</color>
<color name="Salmon">#FA8072</color>
<color name="GhostWhite">#F8F8FF</color>
<color name="MintCream">#F5FFFA</color>
<color name="WhiteSmoke">#F5F5F5</color>
<color name="Beige">#F5F5DC</color>
<color name="Wheat">#F5DEB3</color>
<color name="SandyBrown">#F4A460</color>
<color name="Azure">#F0FFFF</color>
<color name="Honeydew">#F0FFF0</color>
<color name="AliceBlue">#F0F8FF</color>
<color name="Khaki">#F0E68C</color>
<color name="LightCoral">#F08080</color>
<color name="PaleGoldenrod">#EEE8AA</color>
<color name="Violet">#EE82EE</color>
<color name="DarkSalmon">#E9967A</color>
<color name="Lavender">#E6E6FA</color>
<color name="LightCyan">#E0FFFF</color>
<color name="BurlyWood">#DEB887</color>
<color name="Plum">#DDA0DD</color>
<color name="Gainsboro">#DCDCDC</color>
<color name="Crimson">#DC143C</color>
<color name="PaleVioletRed">#DB7093</color>
<color name="Goldenrod">#DAA520</color>
<color name="Orchid">#DA70D6</color>
<color name="Thistle">#D8BFD8</color>
<color name="LightGrey">#D3D3D3</color>
<color name="Tan">#D2B48C</color>
<color name="Chocolate">#D2691E</color>
<color name="Peru">#CD853F</color>
<color name="IndianRed">#CD5C5C</color>
<color name="MediumVioletRed">#C71585</color>
<color name="Silver">#C0C0C0</color>
<color name="DarkKhaki">#BDB76B</color>
<color name="RosyBrown">#BC8F8F</color>
<color name="MediumOrchid">#BA55D3</color>
<color name="DarkGoldenrod">#B8860B</color>
<color name="FireBrick">#B22222</color>
<color name="PowderBlue">#B0E0E6</color>
<color name="LightSteelBlue">#B0C4DE</color>
<color name="PaleTurquoise">#AFEEEE</color>
<color name="GreenYellow">#ADFF2F</color>
<color name="LightBlue">#ADD8E6</color>
<color name="DarkGray">#A9A9A9</color>
<color name="Brown">#A52A2A</color>
<color name="Sienna">#A0522D</color>
<color name="YellowGreen">#9ACD32</color>
<color name="DarkOrchid">#9932CC</color>
<color name="PaleGreen">#98FB98</color>
<color name="DarkViolet">#9400D3</color>
<color name="MediumPurple">#9370DB</color>
<color name="LightGreen">#90EE90</color>
<color name="DarkSeaGreen">#8FBC8F</color>
<color name="SaddleBrown">#8B4513</color>
<color name="DarkMagenta">#8B008B</color>
<color name="DarkRed">#8B0000</color>
<color name="BlueViolet">#8A2BE2</color>
<color name="LightSkyBlue">#87CEFA</color>
<color name="SkyBlue">#87CEEB</color>
<color name="Gray">#808080</color>
<color name="Olive">#808000</color>
<color name="Purple">#800080</color>
<color name="Maroon">#800000</color>
<color name="Aquamarine">#7FFFD4</color>
<color name="Chartreuse">#7FFF00</color>
<color name="LawnGreen">#7CFC00</color>
<color name="MediumSlateBlue">#7B68EE</color>
<color name="LightSlateGray">#778899</color>
<color name="SlateGray">#708090</color>
<color name="OliveDrab">#6B8E23</color>
<color name="SlateBlue">#6A5ACD</color>
<color name="DimGray">#696969</color>
<color name="MediumAquamarine">#66CDAA</color>
<color name="CornflowerBlue">#6495ED</color>
<color name="CadetBlue">#5F9EA0</color>
<color name="DarkOliveGreen">#556B2F</color>
<color name="Indigo">#4B0082</color>
<color name="MediumTurquoise">#48D1CC</color>
<color name="DarkSlateBlue">#483D8B</color>
<color name="SteelBlue">#4682B4</color>
<color name="RoyalBlue">#4169E1</color>
<color name="Turquoise">#40E0D0</color>
<color name="MediumSeaGreen">#3CB371</color>
<color name="LimeGreen">#32CD32</color>
<color name="DarkSlateGray">#2F4F4F</color>
<color name="SeaGreen">#2E8B57</color>
<color name="ForestGreen">#228B22</color>
<color name="LightSeaGreen">#20B2AA</color>
<color name="DodgerBlue">#1E90FF</color>
<color name="MidnightBlue">#191970</color>
<color name="Aqua">#00FFFF</color>
<color name="Cyan">#00FFFF</color>
<color name="SpringGreen">#00FF7F</color>
<color name="Lime">#00FF00</color>
<color name="MediumSpringGreen">#00FA9A</color>
<color name="DarkTurquoise">#00CED1</color>
<color name="DeepSkyBlue">#00BFFF</color>
<color name="DarkCyan">#008B8B</color>
<color name="Teal">#008080</color>
<color name="Green">#008000</color>
<color name="DarkGreen">#006400</color>
<color name="Blue">#0000FF</color>
<color name="MediumBlue">#0000CD</color>
<color name="DarkBlue">#00008B</color>
<color name="Navy">#000080</color>
<color name="Black">#000000</color>
</resources>

Changing the holo look and 9png editing:

Well if you had seen, you could have notice that if you run your theme, it will have kind of holo look. Its because of the pngs and .9.pngs present in res/drawable-xhdpi folder. As I mentioned, you should have some good photo editing software for this job since not all photo editors out there provide good 9png editing. You can search on how to edit the 9pngs properly and get your desired colour. Check the below links for reference-

http://developer.android.com/guide/developing/tools/draw9patch.html

http://developer.android.com/guide/topics/graphics/2d-graphics.html#nine-patch

NOW that this is done completely, next part is to test, sign and release your theme on google play.