Be flexible and have fun. I think you'll find a consensus that that's one of the best parts of a solo trip, being able to slow down and smell the roses. If you hear live music playing, go looking for it - I found the Main St Philharmonic and British Revolution completely by accident.
I don't know if you have any ADRs, but I'm a big champion of "don't be shy about eating alone." Also, don't be shy about meeting characters alone.
If you've never done Animation Academy at DHS (and even if you have), it's a lot of fun - you will learn to draw a Disney character. Even if you think you can't draw, just relax and follow along and you might be surprised at how well your drawing turns out.
Edit to add: Two more general "been there done that" tips: If the day is cold, do not go to AK. Not all the animals will be out on the safari and walking trails. (For example, a CM said the bats at Maharajah Jungle Trek can't come out if it's under 55 degrees.) Kali River Rapids will also be closed if it's too cold.
And be sure you have fresh/fully charged batteries for your camera. Had to take a break on my DHS day when my camera died. Luckily I was at BC, but it was still an unplanned detour on the day.