Much easier and more exact if you check out NADA.com or KBB.com. They take into consideration options, mileage, condition, and many other factors. Keep in mind that when someone comes to see your vehicle, they are also going to check NADA or KBB so your price should be very close to theirs. I normally tell people to check both and pick the higher price if you are a seller. Then if someone questions your price, you can refer them to KBB or NADA to show them you are right on the mark. The method above will do much better should someone question your price than saying you got the price from some guy on some website.
A vehicle is only worth what someone is willing to pay. Yes, start a bit higher and negotiate down a bit. I would also suggest:
1) Get a complete detail
2) Get a CARfax to show people (so they don't have to spend $20 each to check your car)
3) Make sure you have the title and a bill of sale ready to go.
4) If you live in an inspection state, get an inspection on the vehicle.
The easier you make it for the buyer, the more likely they will buy.