keep layering till the track sounds really full.
best bet is to first make a catchy bassline. Then layer subtle basses to it. basses on different freqs. when your bassline is full sounding and rich with bass response, pleasing to listen to on it's own, leave it and bounce it to a wav.
With beats you need to make the basic bones yourself. (read zeal's tutorial in production, follow to the last word and you'll be making amazing drum loops)
When your beats sound as full as a whole track, then you are ready.
start a new tune with your bounced bassline and your beats (bounced too).
eq them together, so they sound good together. mix down your track with just these two elements. Your beats and bass will provide the catch and all of the low end for your track. when you have just two samples that sound phat running together. Then you can add xtra subtle breaks and fx, make sure you cut out any low freqs. If your bass sounds a little off, try lowering the low end on your break.
When making a bassline... I use usually about three different basses. i arrange them together as one pattern, each in it's own mixer channel with fx. When it sounds good. i solo each bass sound and export each element as its own wav. On my track i have three different wavs to make one bassline. I assign easch element to its own mixer track so i can fine adjust the bassline in the final mix.
what you should end up with is two parts of your tune (drums and bass...funnily enuff)
It should almost sound like a finished tune, quality wise. Then add an intro, samples and fills.
mixdown as you go. Dont add anything till you have mixed down what you have already.
and keep listening to tunes, analyse the basslines, try pick out the elements (sub, distorted subs, mid basses.) hazzards tunes are good for this.
hope this helps my friend.
peace