1. If your wheels are the same width as stock, then the offset should be as close to stock to keep the wheels from being pulled in or pushed out.

2. Spacers are fine IF they are hub-centric spacers. Anything less is putting the load on the lug bolts.

3. If your wheels are wider than stock, then you have to figure a whole new offset to make sure your rims are still centered compared to the stock ones without pushing them out from the center of the car too much. This could lead to rubbing the edges of the fender and possibly cutting into the edge of your tires.

4. Wider wheels should be complimented by wider tires. Not always, but it looks a little strange on a wheel that is wider to have the stock width tires. I know I had stock size tires on my rims and they were a half inch wider in the front and one inch wider in the rear. Needless to say the tires seemed really narrow in comparison.

Lastly, examining all these things together with your wheel styles will allow you to pick the correct combination and spacers (if needed) ahead of time.

Just curious, what are the specifications on the wheels and tires you are considering?