There are many ways to organize your tunes. iTunes does a good job a doing all the filing for you, Then you have figure out what works for you. Ean has several older blog posts about how he does this. Here’s one.
There is also a sticky thread at Native Instruments Forums about it HERE
And a search of this forum will also bring up some relevant threads where this has been dicussed with different options and software.
Beat gridding your tracks enables you to use the sync button, makes your time synced Fx stay on beat, makes it easier to drop cues on beat(if snap is enabled), enables you to use the mouse to click ahead in the song with it staying in sync, makes your loops drop on the 1 count(if snap is enabled)
Once again there are tutorials about this in older blog posts, and in the forum. As well as videos on the blog and youtube about how to do this.
I think manual playlists are the best. The wider your taste in music - the trickier it can be to make it flow right. You don’t want to spend a lot of time cocking about finding tracks. Group them, stick them in playlists. Commit to like 30-40 tracks in a set, knowing you may not touch half of them. Seems more reasonable to me than having 50 gigs of tunes at your finger tips.
The new version of Traktor will apparently have ‘Full iTunes integration’ which sounds interesting.
And when it comes to beat grids, read the Traktor manual and do a forum search because that will be a lot quicker and easier than someone writing out a full explanation again