There are several things you can try in your search for that game you can't remember the title of:
1. Use online game databases.
MobyGames, Universal Videogame List, Giant Bomb and other websites provide exhaustive databases of video games for various platforms. While they're not all-encompassing, there's a good chance your game will be listed.
Some websites provide powerful yet easy to use search engines, like MobyGames' Game Browser which allows to specify search criteria such as platform, genre or perspective.
Wikipedia also has numerous lists of video games, although they might be not as easy to browse.
2. Ask here at the DOS Games Discussion Forums.
The Find Old Games sub-forum is the place to ask other users for help in identifying a game.
VERY IMPORTANT NOTE: We regular users of the DOS Games Discussion Forums are always happy to help finding your old game, but our knowledge of video games is not all-encompassing. We have a passion for DOS games, and old games for other systems -- "old" here means games from 1980s and 1990s, early 2000s max. If your game was released some years ago, but after ca. 2005, please consider asking about it elsewhere, e.g. at the Tip of my Joystick subreddit:
https://www.reddit.com/r/tipofmyjoystick/
IMPORTANT NOTE: Before posting a help request, please read the posting guidelines very carefully.
Properly formulating a request will increase the chances of quick and successful identification. By following the simple guidelines, you help others help you in finding your game.
Avoid common help request posting mistakes that make it harder to help you. Always:
1) Give your thread a descriptive title: Sci-fi fighting ants around 1995, not please help!
2) Tell us which computer platform (DOS, Windows, Playstation, Atari, etc.), around the year you played (In high school, so must be around 1995), and what you recall about playing it (guy jumping and climbing around a screen. It was mostly black background. bad guys were monkeys, I think. I played multiplayer with my brother and with both joysticks and keyboard)
3) Make a separate thread for each game. (It's OK! We prefer it that way!)
Please refer to the posting guidelines for more detailed information. Also do not forget that the General Forum Rules also apply in full to the posts made in the Find Old Games sub-forum.
3. Try other search methods.
While you're waiting for a reply, you can try finding your game by other means. Here's a couple of useful tricks:
o Use other databases and wikis.
Check various game-related sites and Wikis which can provide useful information.
o If you're trying to find an old PC game, you can try sites from this list which is about classic PC gaming.
o GameFAQs is a large database of FAQs, walkthroughs, cheats etc. for games on various platforms.
o Wikis like TVTropes have a lot of in-depth information about video games.
o Use the Google Image Search trick. [suggested by Quadko]
Go to images.google.com
Search for keywords like:
* DOS Screenshot CGA
* Windows Screenshot tank battle 2D
Try some different keywords, whatever you remember about the game. Words like "Screenshot" and "Game" and "Dos" sometimes helps filter down to useful game lists.
o Use a search engine that finds similar games.
GameDipper is an experimental search engine that analyses keywords to find similar games. It does not always yield accurate results but it can provide some leads for further search.