My 2 cents (except we don't have pennies in Canada anymore) and sorry for the length:
The first rule is NEVER, EVER back into a site if there are kids around and even adults unless you know for sure there is nobody around. You do not want to run over anyone or some kid's bike. Always use a spotter. If DW or DH isn't there with you, then ask for help. You cannot see a dang thing behind your TT.
The second rule (well, my rule anyway) is if you have been driving all day and are really tired and hungry, try and find somewhere in the CG you can stop without interfering with anyone and take a break. Have a bite to eat maybe. Walk around a bit or sit down somewhere. Take a bathroom break if needed. Then when you are feeling more composed and refreshed, then back into your site and set up. I find this can really help and make things easier, especially if it's a more challenging site. Might just be me though.
In the beginning, I would find a big empty parking lot and practice. Depending on your trailer's length, I think one of the hardest things to learn is how much past a site to pull and exactly when to start cranking over the steering wheel and how much. If you get it right, it's easy-peasy but if you mess it up, it can take a lot of time and effort to get in.
When you get to your destination, if other campers or a CG host come running out to help, politely tell them you are okay doing it yourself. These helpers can really mess you up... If you are tired, you may not be focused enough. It's a good idea to get out anyway and see where the pedestal and sewer hookup are and if there are obstructions like trees, branches, big rocks, etc. If you have a slide(s), you need to ensure you have enough room for it. Don't forget when you are all the way in or nearly in, you may need to put levelling blocks under the wheels on one side and may need to pull forward a bit and then back fully in.
Use your other half (usually female for some reason) as a spotter. Walkie-talkies can really help. Cheap at Best Buy.
With your other half, go over how you want hand signals to work. Very important! If your TT and TV are not in a straight line, the spotter needs to be on the side that has the clear line of vision to the rear and the spotter needs to be visible. If you swing in the opposite direction, the spotter needs to move to the other side pdq. If you can't see your spotter, do not move. The spotter really needs to understand all this. The spotter should point in the direction the rear of the TT needs to go and the driver needs to learn which way is which when looking in a mirror. The spotter should alternate between motioning you to move in a straight line or which way to turn and how much there is left to back up. Hands far apart means LOTS of room left, hands/fingers close together means almost no room left. Getting your hand signals co-ordinated and understood really helps a lot. (Ask me how I know...)
You don't always have a choice of which way you have to back into a site. You need to learn how much forward you need to pull past the site before you starting backing up and swinging around. When first learning, you may need to get out numerous times to learn where you are really at versus where you think you are. Many CGs have all sorts of obstructions too and some have weird angles to back into. If you are having trouble backing up, get out and survey the situation. You may even need to pull all the way out and well forward and start all over.
Some CGs have the water,sewer and power spread out quite a bit and you may not be able to get exactly where you want. This is another reason to scope things out before you start backing in. We were in a Thousand Trails a few days ago and the pedestal was nearly 50' from where the water and sewer was. Fortunately we carry a spare 25' 30 amp shore power cord and an adapter to make up 50'. Some sites have the sewer hookup at ridiculous elevations so that they will barely drain, if at all. Sometimes a CG pedestal may be in really bad shape or even not working. Once in a while, you may find it's just better to find another site in the CG.
Don't always assume that by looking at a CG's site layout map that it will be easy to get into the site you want. We were at a KOA 2 years ago and the only way we could get into one of the few remaining sites was to back in about 1/8 mile along a winding up and down road. We drove 1/2 way in first before finding out you could not turn around. It was crazy. Fortunately that was when we had our old 20' TT and regular cab truck.
Another tip is if you have a choice of sites, before going through all the effort of backing up, try and scope out your neighbors. You may not want to be next to a noisy dog, screaming kids, a chain smoker or loud music. (BTDT) Of course, it's not always possible to tell beforehand.
And when you are finally stopped where you want, the first thing you should do is put your wheel chocks in. Do not unhook chains or hitch until you have done this. If other campers and people are still hanging around, wait until they are gone because they can really distract you. (Another "ask me how I know" thing...)