The amount of time you rest between sets can significantly affect your results. Rest up to three minutes between sets if pure strength development is your priority, and one to two minutes if muscular endurance and tone is your priority. Three minutes permits the muscles to recover from fatigue so that you can generate enough energy to perform another maximal lift on the next set. Benefits are not discreet. That is, there is carryover from one style to another, so that if you rest just one minute between sets, you will still increase endurance and tone, and if you rest three minutes between sets, you will still gain endurance and tone. I recommend one to two minutes for most people. More than that and you may end up spending more time chatting with others in the gym than getting down to what you're lifting for in the first place, that is, getting stronger. The guiding principal with weight lifting is volume. That is, the equation sets x reps x weight (in pounds). You can see that the more work you do the more benefit there is. If you take a lot more time resting than lifting, then you minimize your benefits. Take breaks between sets for sure, but get back to work as soon as the muscles are rested.