[Samsung Galaxy W I8150] hotheabilly:
Requirements:

Follow the simple instructions here.

You MUST be rooted

You should be running a custom recovery like ClockWorkMod Recovery (CWM) or Team Win Recovery Project (TWRP). I use CWM, so this guide is based on that.

Your device must be using ARMv7 CPU architecture. If you aren't sure what that is, check this thread.

You must have a file explorer that has root permissions. I use ES File Explorer, so this guide is based on that.

You need at least 60MB of system space for the full offline installation. (30MB for online only version) If you don't know how to check, simply download Titanium Backup from the market. It tells you right on the main screen.

If you are not a noob and know what to do already, please skip this. The permissions are listed at the bottom for easy reference, should you need them.

INSTRUCTIONS:

- Download whichever zip you want. If you need to save /system space, download the the smaller, online-only package, otherwise get the normal one for the full experience. There is also a version of each which removes the "double-take" condition of the app. This is where it loads the results twice. The one that loads the results twice formats search results properly on the first try, but does not auto launch some cards. The non-double-take version may not format some search results properly, but auto launches tasks such as navigation and texting. Choose whichever one you prefer. If you have questions, please don't quote this entire post. Simply edit out the part you have a question about.

Update: Each version listed has the full version and the Offline only version. Pick the one you want and flash it. If you aren't sure which one to use, or if this is too much information or is otherwise overwhelming for you, just flash the M7 version - Offline/Online, since it's the latest. Be sure to scroll down a bit and read about it, though.

Before doing anything, you need to make sure you have at least 60MB of free space on your /system partition for Offline/Online files and 30MB of free /system space for Online Only files.​

Flashable ZIPs

[*]M7 - mikeyxda's version 7. This version improves on M6 by tweaking notifications to be more accurate and frequent. This version may use more battery. If you are using a Sense ROM, see the troubleshooting below for a hack to improve Google Now performance and battery efficiency.

Online/Offline via Mediafire - 36.48MB /Hotfile mirror

Online Only via Mediafire - 14.06MB /Hotfile mirror

M7 Update - 3.97MB /Hotfile mirror

M7-Velvet.apk Only

[*]Inverted M7 - This is identical to the M7 files from above, except the colors are inverted, so that it has a black background instead of white, and white text instead of black. If you already have Google Now flashed, you can simply perform the update to this version.

Online/Offline via Mediafire - 36.81MB /Hotfile mirror

Online Only via Mediafire - 14.04MB /Hotfile mirror

Inverted M7 Update - 4.30MB /Hotfile mirror

M7inverted-Velvet.apk Only

[*]M6 - Mikeyxda's version 6. This version has improved on the previous one by fixing the double take problem, typed searches are working, auto launch is fixed, as well as the following fixes from the previous version: Red mic with cards showing with no refresh needed, no FCs, offline dictation, and no stretched words. These zips all use zipalligned apks.

Offline/Online via Mediafire - 36.43MB /Hotfile mirror

Online only via Mediafire - 14.01MB /Hotfile mirror

M6 Update - 3.92MB /Hotfile mirror

M6-Velvet.apk Only

[*]R3 - "Nearly there" version by ReekoTubbs. This version has the Red mic with cards showing with no refresh needed, no double take, no FCs, offline dictation, auto-launch, no blank screen, and no stretched words. These zips all use zipalligned apks.

Offline/Online via Mediafire - 36.48MB /Hotfile mirror

Online only via Mediafire - 14.07MB /Hotfile mirror

R3 Update - 3.97MB /Hotfile mirror

R3-Velvet.apk Only

How to:

- Move the file you picked to the root of your SD card. Don't put it in any folder. This just makes it easier to find.

- Reboot your device into recovery. See your device's specific instructions on how to do this if you are not sure. Google it for a faster answer.

- In CWM, navigate to "Install zip from SD" and select that.

- Next, highlight "Choose zip from SD card" and select it.

- Scroll down to the Google Now zip you loaded onto your SD card, then select it.

- Scroll down and select the option that says "Yes - Install Google Now....zip"

- Once it has flashed, go back to the main CWM menu and select "Reboot system now".

Double Checking:

- Let the ROM boot all the way, then fire up ES File Explorer (or whichever one you feel like using). We need to make sure a few permissions stuck (just in case).

- If you haven't used ES File Explorer before, open it, then hit menu.

Tap settings, then scroll all the way down.

Check the box that says "Up to Root" (pic).

Then check the box that says "Root Explorer"

Allow root access when the dialogue box for Superuser pops up.

After that, check off "Mount file system", then back out of the menu. (pic)

- Navigate to /system/usr/srec/ and find two folders named "config" and "en-US"

- Tap and hold on the "config" folder icon to bring up the options menu, then scroll down to Properties.

- Tap properties, then tap change and see if the check boxes match this picture.

- If it matches, leave it alone and head back to your home screen to enjoy using Google Now! If it doesn't match, change it so it does.

- Do the same thing for the "en-US" folder.

- Go into the settings menu for Google Now and set it up for your Google account and various other settings.

Now What?

So, you flashed Google Now. You're wondering what you can do with it, right? Well, thankfully, Killer-B has a handy little guide to get you up to speed on all the cool stuff Google Now can do as well as how to do it!

Commands & Now Cards For Google Now!!! Now Video, and custom widget

Troubleshooting

1.) The red mic screen won't display.

To fix this, press the normal mic within the Google Now app. While it is listening (after it beeps), press menu > refresh. Now you're at the red mic.

2.) Can't exit the Google Now app with the back button.

Use the Home button.

3.) Google Now Force Closes.

Make sure you have enough space on your /system partition before installing this. You need at least 60MB free for the Offline versions and 30MB free for the Online versions.

4.) Sports cards aren't showing up.

It won't add teams that aren't in season. American football is currently in preseason. Baseball, however, works perfectly fine.

5.) I want Google Now in another language than US English.

From the Google Now home screen with the cards, tap Menu, then Settings. Tap Voice, then Language and select the language you want recognized. The text of Google Now in searches and regular cards should mirror that of your system language.

6.) My phone exploded.

Have a muffin.

If, for some reason, you want to remove Google Now and return to how you were before, flash the following zip. It removes all Google Now files, and returns the original Google Search app and voice files, as well as sets permissions for the Search app.

Google Now to Google Search via Mediafire- 629.35KB /Hotfile mirror

Please don't thank me. Find one of these guys' posts and thank them. They made it happen, not me.

reekotubbs, MikeyXda, Lenny_kano

all credit goes to this thread: http://xdaforums.com/showpost.php?p=29756226&postcount=2856