I can recommend following actions as steps that can directly influence your game's stability, they won't always work, but are worth trying:
0) Absolutely necessary - run the game as administrator or you'll experience fatal graphics errors, CTDs and other issues (particularly on Win7 and Vista).
Short How-to on fixing this:
Right-click TATW icon, choose Properties, choose Shortcut tab, click Advanced, tick "Run as administrator", then click "ok".
1) delete all map.rwm files from data\world\maps\ - do that each time after updating mod files
2) delete strings.bin files from data\text\ folder - rarely necessary
3) disable file cache - fixes old savegames
Spoiler Alert, click show to read:
Additional common CTD solutions:
4) disable the advisor - crucial to maintain battle stability
5) turn UAC (User Account Control) off if using Vista/Win 7 and proceed to step 6 - absolutely necessary to keep any stability
6) reinstall MTW/TATW
7) turn autosaving off - may help in getting rid of campaign map CTDs
Other means of keeping good stability:
8) reinstall graphics card drivers
9) don't use multiple submods without making sure they're compatible
Extended info on disabling UAC in Vista\Win 7:
a. Win 7 - Press Start, write "UAC" in search window, "Change User Account Control settings" should be found - click it.
Move the slider downwards to "never notify" position.
b. Vista - Try Win 7 method, but untick "Use User Account Control..."; alternatively you can go to main User Accounts page in Control Panel, click "Change Security Settings" and then untick beforementioned element.
c. Press "OK". (You must restart your computer for UAC to be disabled.)
d. I recommend uninstalling TATW and making sure Third_Age\data directory is deleted (you can keep saves, preferences etc).
e. Find compatibility folder and delete it, make sure you backup any savegames found there (there might be no saves inside as well):
C:\Users\YourUserName\AppData\Local\VirtualStore\Program Files\Sega\Medieval2 Total War (default path, could differ a bit)
f. Install TATW following usual routine.
g. For players confident that they installed correctly: skip uninstalling part and go straight from "c" to "e".