I am in the middle of doing this with one of my bikes. For "conventional" screw in bottom brackets with spindles, the things you need to consider are: 1) Shell width 2) Thread standard 3) Taper standard 4) Spindle length.

If you're keeping your current crankset it should be an easy process. Buy a bottom bracket that has the same dimensions and standards as the current.

If you're changing cranksets things get a little sketchy. This is what I am going through right now. The taper standard must be compatible and the new crankset will likely require a different spindle length. Hopefully you can find the spindle length dimension for your new cransket online. Otherwise it's a process installing the new crank and determining the required spindle length to get the correct chainline.

Probably reads more daunting than it actually is. Good luck!