In addition to what Blackhorn suggested I would include:
1. Go ahead and apply to the districts that you want to teach...call them the districts where "THE JOB" that you want will be. Even if there is no position open now, at least your credentials will be on file. When a position opens, all you have to do is go back into your application, and officially apply to the job(s). Is that a lot of time filling out applications? Yep. However, HDs, principals, and DFAs like it when potential candidates can tell them that everything they need is already on file at HR before they are contacted. In addition, many districts use the same application program. Once you fill it out for the first district, you can then copy over most of the information from one district to another. Then there are a couple of ESCs (thinking the DFW area) where there is a single application for every school in the service center's area. Fill out one application, and you have applied at every single school in that region.
2. Some online apps won't let you fill out the application unless you apply for a position first. Those applications usually have a generic "HS Teacher" (or MS) option so that they can fill a generic candidate pool. Apply for the generic pool and fill out the application. That way your application is on file, and you can go back and apply for the band positions when they open.
3. Especially in large districts, as what has been said before, HR departments don't know about TMEA or ATSSB. They will only post on the district website. That's why doing steps 1 & 2 are so important...without checking on the district websites, you could miss a good job that never got posted on TMEA or ATSSB.
4. As what has been said before, apply to every job that opens...even if it isn't the most ideal situation. While it might not be *THE* job...*A* job is better than *NO* job; and anyone can handle teaching anywhere for a year or two. *THE* job might want you to have some experience first before they consider you...and you never know, the job you take may end up being THE job after all.