Tes4Mod:OMOD Installation

This is the simplest of the two main mod installation tools, the other being Wrye Bash's BAIN. It is a huge step up from manual installation. If you need to uninstall a mod, it is as simple as right-clicking on the respective OMOD and choosing "deactivate." If another mod is using some of the files that the uninstalled mod had used, those will be left in the data folder. A mod's page, at TESNexus or another mod upload site, will usually indicate whether or not it is OMOD-Ready. Most mods will not have any OMOD Info, however.

Intro
OMODs need to be in your OMOD folder in order for OBMM to detect them. If you download an OMOD to another folder, double-click on it: OBMM will be launched and move the OMOD to the necessary folder.

If you batch activate OMODs, you will not be prompted to overwrite, so be careful. OBMM batch installs OMODs in the order they appear in the window, so you can use different sort criteria to change the installation order. When sorted by filename, OBMM sorts numerically and alphabetically (numbers first.) With the right numbering scheme, you can implement prioritized installation.

No OMOD Info
This is the state in which most downloaded mod packages will be found.

# Click on 'Create'. (bottom bar)
# Add a mod
#:Notes: 1) most mods are packed in archives, so you will most often use "Add archive" here 2) If mod has OMOD info, it is "OMOD-Ready," and after choosing the target folder or archive, some of the fields of the OMOD window will be filled out automatically. The OMOD conversion data of more complex mods will often add a script as well. 
#* Add archive: add archives (.7z, .rar, .zip)
#* Add files: add loose data files or plugins (.esp, .esm)
#* Add folder: add a folder containing mods' data files or plugins
# Fill out the name, and you can also fill out the version, website, author, group, description, etc.
# Choose "Edit script" to modify or add a script to facilitate installation.
#:Notes: if you download an OMOD script or OMOD installer, it is usually packed in an OMOD conversion file, so you can just use the "Add archive" function, and the script will be filled in for you.  (Take note of the two radio buttons near the bottom of the OMOD creation window)
# Select the "Data files" option. In general, file paths should begin with one of the common mod folders.
#:Notes: see Intro to Mods if you are not sure what qualifies as a "common mod folder"
# Once the OMOD's information is filled out, create it by choosing "Create omod" in the bottom-right corner.

thumb|none|370x280px|'Plugins' radio button is checked on the left; 'Data Files' is selected on the right.*sanity check (Streamline)*

OMOD-Ready

# Click on "Create" (bottom bar)
# Use "Add archive," and navigate to the OMOD-ready archive.
# Click "Create omod"

OMOD

# Double-click on the OMOD in Windows Explorer or 'Open' it, or put/extract the OMOD file in to your OMODs folder. (The default location is  .)
# Double-click on the OMOD in the OBMM window, or select the OMOD, and choose "activate" (bottom bar.)

See Also
Oblivion Mod Manager

External Links
ABO's OMOD Collection - TESNexus <-- ABO uploaded OMOD versions and OMOD conversion data for various mods
BAIN vs. OBMM - UESPWiki
How To Create an OMOD - TESCSWiki <-- more in-depth description of the OMOD creation process targeted at mod makers
LHammond's TESCS Wiki Page - direct links to many of LHammond's tutorials
OBMM HowTo - LHammond's OBMM website <-- has many, many tutorials and other useful OBMM info
OBMM HowTo - Script Analyzer - LHammond's OBMM HowTo website
OBMM HowTo - Tutorials - LHammond's OBMM HowTo website
OBMM ReadMe
Search "OMOD Installer" - TESNexus <-- search for OMOD scripts
Search for "OBMM Script" - TESNexus <-- search for omod scripts
Search for "OMOD Conversion Data" - TESNexus <-- search for OMOD scripts
Search for "OMOD Info" - TESNexus <-- search for OMOD scripts
Timeslip's Oblivion utilities and mods