I agree with Kary, that each situation is different as is every buyer, so a good working knowledge of what each one does, the timeframe attached and the way it may overlap with others is required to do the best possible job..
I agree with the other posters that you need to review your situation with your agent to determine which contingencies are appropriate in your situation.
3. Credit toward closing and prepaids
4. Inspection of entire premises, including but not limited to radon, radium, well, well water, well, septic....
5. Closing date and many more.
6. Occupancy date
7. And many more.
Some of the above are required in our state by most lenders and others are not. In most cases, the more contingencies you put in your offer, the less likely the seller is going to accept. Sellers like clean unencumbered offers. That said, you need to protect your investment before you buy so buyer beware.
What we're seeing in Seattle is that it's becoming such a bidding war that many buyers are waiving contingencies to make their offers more attractive to the seller. Although it's entirely buyer discretion, I always encourage my clients to make a contingent offer, if they can. I'd rather not win the offer than have a client buy a property with major unresolved issues.