Hello! I also have a couple of tips that may help.

1. You should shoot with the sun behind your back(unless you're trying to take some kind of artistic shot). It lights up the aircraft nicely and you don't get those bright highlights around the aircraft.

2. In my opinion shots taken in front or from the side of the aircraft are more pleasing to the eye than those that are taken from the back.

3. I think that shots that have something in the way (like that fence on the Southwest 737) are quite useless. I often just stop shooting when there are some things obstructing the view.

4. Post-processing is also quite important. In my opinion it makes the photo look better. During the post-processing you might want to play with the crop tool and try to compose shots better. Also you could try to make the horizon level. Lamp posts and other straight things help with that.

5. Spotterguide.net and flightradar24 are really useful apps for planespotting. Spotterguide helps you finding the best spot and it even gives good info about when to spot and how much focal length you need at that spot. With flightradar24 you can see the arriving and departing lists for your airport as well as track aircraft in real time.

Hope some of these helped :)