Typically this is the (or "a typical") process:
1) Work the song progression out in your head before you start. Record some scratch mixes without drums, or maybe just with your drum machine. It's often a good idea to be able to play your entire song through on an acoustic guitar, for instance, before starting to record anything. That way you're certain to have a good working knowledge of your new song.
2) Either create a drum track, or create a click track in the drum software you want to use. You need *something* to keep time or it becomes exceptionally hard to use software to create your drum track. Export the drum or click track to a single scratch wave. Remember to include lead-in clicks, and you'll want clicks ANY TIME there is a break in the drums, it'll make your life much easier. It is best to use a seperate sample or track in your drum software for the click, even if you're using the same hi-hat sample from the rest of your song. You'll see why later.
3) Import the drum or click track into your multi-track software, and use it to guide you as you record some portion of the rhythm to get things going, usually bass guitar and rythym guitar. You're now working on the physical song structure, and by the time you're done with this step, you should be happy with the direction your song is taking. This may require repeating steps 1-2 to some extent.
4) Work out more of the drums, each time still exporting a single wave.
5) While perhaps in the process of #4, you'll also be redoing your rhythm tracks. As you change the drums, it will change the dynamics of the song, and will effect the way you want to be playing your various instruments. Maybe add some scratch vocals to see how things fit.
6) Eventually you'll end up with a solid drum track and a good rhythm section. At this point you can start adding your leads and all the gloss. Your still working with the single drum track, but it should be enough to get you there for now.
7) When you start nearing completion of the project, it's time to mix your drums right. Make absolutely sure you're using the right samples for the job, then set each sample to play CENTER and at 100% VOLUME. Then you're going to export each drum to its own wave file so that you can properly mix the drums in with the rest of your song. In fruity, for example, you'll mute all but one of the drums, and do an export. Then you'll mute all but the next drum, and export. And so on and so forth. The reason you used a seperate sample/track for the click is that it's going to be very easy to mute the click track when you start getting close to final mix time. Otherwise you'd have to go in and manually mute the hat (if that's what you used) at the appropriate times...a pain.
To answer your questions:
Yes, almost every drum/sampling software package on the planet that I'm aware of can import wave files. This is one reason why software in the right hands can often kick the crap out of most drum machines. Flexibility and the opportunity to start with better sounds.
Fruity loops is a very static beat oriented editor. It allows you to define infinite "patterns" consisting of one or more samples. You then trigger each sample by clicking a little box representing the appropriate time. So for instance you tell fruity that you want to work with patterns of say 32 (or whatever) beats. Fruity creates a pattern view consisting of the samples you're using, followed by 32 little boxes. You then set the beats per minute, and start selecting boxes which represent sample triggers. It's very straight forward and easy to use, but like somebody already stated in this thread, it's basically limited to that within one song. You can't do time signature changes, which is one thing that most sequencer software packages are lacking. Fruity is a wonderful tool to own though. It has a boat load of great and interesting features, like a piano roll editor. This all works with your predefined samples and does not require MIDI.
Want to hear some fruity examples, visit my website at
http://www.slackmaster2000.com and listen to "Monday" and "Thursday". The drums in Monday were done entirely in fruity loops using my own samples. Thursday is a piano piece that was created completely note for note with the fruity loops piano roll editor and some grand piano wave samples I downloaded (there is of course a major lofi effect over the entire piece). I know it's not drums, but maybe it'll give you an idea of what fruity is capable of in the hands of an amature.
Slackmaster 2000
Monday is at the top of my mp3 playlist! I've actually been trying to figure out that solo. I'm not to experienced on guitar, so it's a pretty ambitious undertaking for me. I'm not even past the first lick. Maybe this would make a good thread in the guitar clinic! LOL! NO, wait a minute, seriously, ....
And if some pro uses effects which one and how much reverb or chorus do you prefer?
...anyway, I find fruityloops to be a powerfull drum machine/sequencer/instrument...I use it for more than drums...but try not to. hope this helped a little.