1. Chimney MUST be cleaned before use (preferably each season, but in this case you have no idea the last time someone burned something in it and you have no idea what they may have burned). A real chimney sweep will also make sure none of the fire-bricks are loose and can tell you if you have any reason to be concerned about the condition of the chimney and its various parts. In my area of the midwest, a thorough cleaning runs about $60.
2. Have someone SHOW you how to open and close the flue. This is essential!
3. @Seek_Kolinahr is absolutely correct you don’t want to burn pressure treated lumber, anything that has been painted, and you really want to take it easy on woods like pine that are very “sappy” as they can increase the build up of creosote in the chimney.
4. The easiest thing is to have someone SHOW you how to lay a fire, start it, etc. There are fire starters available commercially (make sure the one you pick is designed for an interior fireplace and not to start fires outside). Just remember that fires need air to burn. As you put the wood into the firebox, there should be a heavy metal grate onto which you will put it (this allows air to get underneath the wood). You need to start small (twigs etc are called tinder and are used to start the fire). Then you add kindling (starting with small branches about as big as your thumb in diameter and working up to as big as your arm in diameter). The big logs are called fuel and they go on last after the fire is established using the smaller wood.
5. See if your fireplace has a gas starter and have someone show you how to use it. It can be a little scary the first time.
6. DO NOT start a fire unless you have fireplace tools available. You need to be able to move the wood around as the fire burns and there is no substitute for a good set of tools.
7. It is also critical that you have a way of closing off the fire from the room—even if it is a chain-link screen, you don’t want to have to sit next to the fire until it is cool (could be up all night). If it has glass doors, even better.
8. Having a fire extinguisher nearby is excellent but make sure it is for wood fires and make sure you know how to use it should you need to. I have seen people with a working fire extinguisher who had no idea how to make it go. If you need it, follow the instructions on the side of the extinguisher for addressing a wood fire (I think it is slow side to side motion).
9. Never leave a fire unattended. Do not leave the house for any reason unless you have a wood stove that is rated and has a door that can be sealed on the front of it (even then it may not be your best move to leave the house particularly if you have pets).
10. This is October, fire prevention month. It would be a perfect time to make sure all of your smoke alarms have working batteries and that they are properly placed near bedrooms etc. so in the worst case scenario, you will be safe.
11. Enjoy your fireplace! Once you have taken care of all the necessary safety features, a fire is a great way to warm up a cool evening, add a romantic feeling to dinner or drinks, and just warms the heart!