In addition to all the good advice above, decide for yourself very clearly what your bottom line is before you post a price. You'll get an amazing variety of offers with infinite variations asking if you'll accept a lower price, pay the shipping, split the Paypal fee, etc. It's fine to be able to factor those things but unless you know what you're willing to accept, it can be maddening.
It's inevitable that someone will make a lower price offer, especially if you mark the ad OBO, but you're not under any obligation to give the person an answer immediately. It usually works well to tell the potential buyer that you'll get back to them if that's the best offer you receive. If they tell you it's 'take it or leave it,' leave it.
It's inevitable that someone will make a lower price offer, especially if you mark the ad OBO, but you're not under any obligation to give the person an answer immediately. It usually works well to tell the potential buyer that you'll get back to them if that's the best offer you receive. If they tell you it's 'take it or leave it,' leave it.