I have to agree with TN. Changing the evaluation parameters is mainly for hobbyists and the programmers themselves.

The default settings are default because the programmers have done extensive testing to determine they're the strongest all-around. Of course, that testing is not exhaustive, and settings could be found to improve strength, but most of the time it's not a promising avenue for casual users.

Changing the evaluation parameters is usually done to force a certain playstyle (such as extreme aggression by tweaking the king safety setting and piece values). However, if you want second opinions for analysis, it's generally easier and more useful to just check with another engine.

One interesting thing to note is that programmers never alter their engines so that they will solve test positions, e.g., positions where you have to find a certain sacrifice or other "best move." It would be nice to solve them, of course, and sometimes using test positions can highlight a latent bug or other oversight, but for the most part, any alterations based on specific positions is counterproductive and detrimental to the overall strength of the engine, as TN says.

So, I am trying to use computers to help me improve at chess. I know I can have the computer analyze my games, but what other techniques are available?

I just downloaded a program called "stockfish", which seems to be pretty strong computer. Just check out computerchess.org.uk for comparisons. So "stockfish" allows you to change how much it values structure, mobility, space, aggressiveness, king safety, defense etc... would it be good to adjust the program to play very aggressively or defensively so as to have a stronger player with varying styles suggesting ways to play positons? The one problem i see is if I change the evaluations at which point will the program begin making errors or pursuing a poor plan to conform to the style I mandate. Has anyone messed around with this sort of function before on this program, stockfish, or other programs?