This applies to regionals, not majors...

Go to a small airport and get current in a light twin, night, instrument, flight review, everything.

Also get some sim time...generic should work, but there are some folks who do company specific sim-prep for certain regional interviews.

Depending on the airlines, 121 and military guys may be able to get a response in a matter of days. I would probably submit your apps in your order of preference a few days apart, and see if you get an immediate response.

If that doesn't work, don't be afraid to interview at multiple companies, the prep is pretty much the same, except the company-specific stuff.

If offered a job at a non-first choice company, accept the job and ask (carefully) for the latest class date available. They may be willing to let you have a later class. If you get a better offer in the meantime, just politely decline the first offer (you don't have to tell them why).

If it comes right down to it, you can always leave in the middle of ground school for a better offer. It happens occasionally, they won't be too upset, and it should not hurt your future prospects.