The previous post above mine is a great point. Not all songs need a great bass line if what you got in the melody and drums is enough to carry the majority of the track.
Now, with that said, this is what I try to fill my beats out.
As stated before, add some fillers of frequency ranges if thats applicable. Ghost notes are great ways of filling in emptiness.
I try to include these pieces into my arrangements.
1 Drums
2 Bass
3 Melodic Instruments
4 Chordal Instruments
5 Vocal Samples
6 (Optional) Chopped Samples
For each of these there should be different patterns, find a structure for you.
In most main stream hip hop, it seems to follow a very vauge structure; 4 bar intro (sometimes half as long or twice as long), 4-8 bar bridge or hook, 16 bar verse, 4 bar hook x 2, 16 bars, 8 bars.
As well, bar 1 of hte verse will also be bar 3, 5, 7, 9, 11, 13. Bar 2, 6, 10, 14 will be your alternate of bar one, meaning add a kick, change up some hi hats, but keep it very similar. All patterns should have slight variations. Bar 4 and 12 are breaks, meaning a couple more kicks and snares to really add flavor. Bars 8 and 16, drops, usually a kick on the downbeat (1st step of 16 steps) and a couple fading hi hats. Keep the drops with no snare and very little kicks or hi hats. This is where the melody should kick up a notch and prepare to drop into the hook, if one is there.
Now the hook can use the same breaks and drops as the verses if so desired. I like to keep them the same, use the break on bar 4 of the hook and the drop on bar 8. I usually create two new drum patterns for the hook. Bar 1,3 and 5, 7 are all the same, while 2 and 6 are alternate hook drums, a lil added spice.
A bridge is completely different than anything else in the song. Its not quite the hook, but its not a verse. This usually means new drum patterns are made, so if you have an 8 bar hook made a new pattern for bar 1, 3, 5, and 7. As well, a new alternate drum pattern for bars 2 and 6. Breaks and drops can be used from the original verse bars, but you can always get creative and change those too, its really up to you.
With all this being said for just the drums, all the pieces listed above (1-6) should all follow the same structure. Its also a good idea to create your patterns based on what they are, like your drums and percussion should each be divided into their appropriate spots, while your melodic ones would have their respective pattern as would your chordal ones.
Hope this helps.
