Different people prefer different ways of rehearsing. Some people enjoy rehearsing at home, this is ok if you don’t have a drummer or stay in the middle of the country and don’t have any neighbours. Other people prefer being in a rehearsal studio as it helps them focus and get on with the job.
If you’re still at school or college there may be the chance of a free room to use for rehearsals. One of the most common places for a lot of bands is a garage, anywhere really where you won’t upset the neighbours.
Other cheap places you can use are local businesses with cellars or spare rooms you may be able to borrow or rent, local pubs may rent out their function rooms during the week, church halls etc. The only downside is that you have to bring all your equipment each time you want to practice. Some rehearsal rooms will rent out equipment and some will also have storage space so you can store some of your own equipment. 

Preparing for a gig is important it’s always advisable to set up as you would on stage. It’ll help you get used to playing without visual cues from each other. One of the most important points is your set list, have it worked out before your final rehearsal. Then you can run through the set and any awkward changes of instruments or patches will show up in time to sort them out. You'll also get a feel for the pace of the set. Obviously running through the set as many times as possible will help.