'96 Grand Cherokee won't start

If the battery has been neglected- corroded terminals, low fluid, top dirty, etc., I'd replace it and start from there.  Otherwise, you need to find the cause of it being drained.  You can do this with a multimeter.  Turn all accessories off, make sure no lights are on (dome light, trunk light, under the hood, etc.).  Set the meter on the highest current setting, and make sure the probes are plugged into the proper slots on the meter.  Disconnect the negative battery cable, and place your meter in between the cable and battery terminal.  It should read less than 50 mA or so.  Switch to the next lower setting until you get a reading.

As far as the starting problem, I bet you've either got a restriction to the fuel system (possibly clogged filter/injectors), or your pump may be getting weak.  It  doesn't seem like an electrical problem.  If you're not sure when the last time your filter was replaced, start with that.