Locking through single-handed isn't a problem, though I was nervous the first 50 times or so. If it's not windy, a single line from the top will do. Someone will usually drop the line to you. Sit on the cockpit edge on the side of your boat away from the wall, giving you a little better leverage holding the boat against the wall. I put out three fenders. If you're alone, ask the lockmaster if you can just float in the middle. When I do, I place my boat in the miiddle of the lock, fore and aft pointed at the sid e walls. This way if the boat starts to drift towards a wall, a little forward or reverse puts you back in the middle. You're very unlikely to drift from the middle all the way to either end.
Depending on what part of the Mississippi you're on, you'll hail locks 1 to 24 on channel 14, 25 to 27 on channel 12. You'll annoy the lockmaster if you call on the radio before you arrive at the lock. When you arrive, try to be as concise in your transmission as you can, e.g. "Lock 5, this is a northbound recreational craft at the entrance, looking for a lift." This way in the fewest words possible, the lockmaster knows what kind of craft you are, where you're located, and what direction you're headed.
There's a traffic signal, red, yellow, and green, at the mouth of the lock, up above the wall. Don't enter the lock, or even approach to within about 150 feet, until the gates are fully open and you see a green light. If you violate this, the lockmaster will have harsh words for you. Don't leave the lock, or even let go of the line if you're on the chamber wall, until you hear the horn sound after the gates are open. Again, rush out too fast and the lockmaster will likely say unkind things. Enter and leave slowly, no more than 3 knots. Keep it slow exiting until you clear the end of the wall, usually 1000 feet or so past the gates. I find it specially annoying to have some huge cruiser boom past me as I'm leaving. Sometimes those guys pay with a citation when they get to the next lock.
Sometimes you'll have to wait an hour or so. Commercial traffic gets priority, and the bigger tows have to be broken down before they'll fit in the lock. This means the lock will have to cycle up and down twice, with the additional time in between to break the barges apart and then put them back together again. I just get off to the side, out of the way, shut off the engines, and throw out the lunch hook.
Relax. After a while it's fun. I enjoy it now, though in the beginning it was scary.