Film on your smart phone. Most smartphones have excellent cameras, so there's no need to spend a ton of money on an expensive camera. Make sure your phone is in Landscape mode (horizontal) for filming.
Use a solid colored backdrop to minimize distraction and clutter. Grey and blue are typically effective options.
Find a quality reader. This is vital and often an overlooked element of self-taping. Your reader doesn't need to be a fellow actor, but they do need to keep the pacing of the scene moving. Having an unfocused reader (or worse, no reader) can be a distraction in the eyes of the casting director.
Use proper lighting. Your tape doesn't need to be professionally lit, just enough that whoever's watching can see your eyes and face clearly. Natural light usually does the trick!
Avoid looking directly into the camera. Place your eyeline slightly to either side of the camera, unless the script specifically calls for you to look directly into the camera (ex: your character is filming a video blog in the scene).
Overuse Props. One or maybe two props can help immerse an actor into the scene, but more than this can cause distraction. Don't worry about supplying the entire set, that's not your job.
Wait until the last minute to submit your tape. Casting directors view tapes as they are submitted. If you have the time, getting your self-tape in before the deadline can go a long way towards casting taking a close look at your performance.
Ignore your acting homework. Remember, the goal of self-tapes are no different from auditioning in the room. You are there to do a job. Make sure to be professional and make choices. As long as you're putting in the work, casting will continue to call you in!