I'm not a big computer person either, but I know what you mean - the only way I've found to reduce the chances of crashing are:
- set as many settings in your game options to as low as you will accept - the graphics demand seems to be a big factor. So set your distance drawing to medium etc.
- Save regularly so that if you do crash you don't lose much.
- When designing, keep things as simple as possible. Try to use as much stuff straight from the catalogue, or if you design stuff, make sure you save it. I'm guessing that a computer having to remember unsaved custom patterns is going to have a hard time.
- Don't overload your lots with too much stuff - the more stuff, and particularly the bigger the family, including animals, the slower things seem to go.
I can't remember much more than that for now, but hopefully someone will come along with some more useful information than I have!