There are many ways you can do this, but this is the easiest to use tool that I've found. bin file so that you can edit it, and then repacks it when you save.
To do so, you'll want to grab the ME3 Coalesced Utility. You can affect the game in fairly signficant ways by modifying this file.
The coalesced.bin file is basically a collection of variables that the game uses to determine different things, from graphical effects to key bindings to things like shield recharge rates.
Warning before you start: I do not recommend using any 'cheats' or a modified Coalesced.bin file if you are going to play multiplayer. Most of the results you find when you Google for how to do a tweak or cheat will tell you which ini file and variable to change, but not exactly HOW to do that. A lot of game tweaks are possible for the PC version of Mass Effect 3, both in terms of graphics and 'cheats', and can be done by editing Coalesced.bin.
