You get to a point, like our band, where we pick 3 cover songs to learn for next practice (usually 6 days apart).
Each person learns their part at home. Generally, if you have been doing this for a while, you can listen to the song. I like to get the tab, also, if ther eis tb. But remember, 3/4 of the tab out there is tabbed by someone who is tone-deaf, so they are generally not correct. They might be correct for the most part, but as a whole they are not. One song might have 6 different tabs. Use the tabs to help speed up the process, but do not rely on them. Now, back to the "you get to a point..." statement. You get to a point that each person learns their piece at home and after playing the song about twice as a band, we have it. Now some arrangements are a bit more difficult with stops, etc...But it sure as hell beats the farting around at practice "jamming" (Which seems to be what everyone thinks is the way to do it) Maybe for the creative process as an original band it works, but definately not as a cover band. Jamming just wastes time and does not help you learn the songs.
By the way, if you are playing covers, learn the song as close to the original as possible. People want to hear it how it is on the radio or the CD, not how you think it should be.