1. A lot of deep house's vibe comes from its rhythm. While the drum patterns don't generally deviate much from the 4/4 template, leaving them straight makes them sound too robotic. To give them a more human feel - à la chris brann's ananda project - you can apply 16th-note swing quantisation or some more sophisticated groove quantisation if your sequencer supports it. Analysing live drum breaks will give you a more human feel than straight quantisation, though you'll probably find that keeping ph production the kicks dead on the beat works best.
2. While programming riffs in ph production and chord progressions with a mouse is convenient if you can't play the keyboard - and handy for tricky stuff, of course - you should at least give the old-fashioned live approach a try. Mistakes can always be corrected later using your sequencer's midi editor, and you might be surprised at how much better your sequences sound when you've played rather than programmed them. Plenty of top producers swear by the 'human touch' to inject a bit of life and soul into their tracks.
3. A very commonly used sound in deep house music is the electric piano. While it's possible to spend hundreds of pounds on a commercial electric piano emulation, there are some superb free plug-ins out there that are more than capable of doing the job. Check out the latest version of mrray if you don't believe us.
4. If you want to create an authentic electric piano sound of ph production, it's crucial that you use the right effects. Check out the kjaerhus classic series - the auto-filter effect in particular can be used to add movement and feeling to an electric piano sound. Start out with the panning notch preset and turn the lfo rate up to around 1.5hz. Then add the kjaerhus delay and reverb plug-ins in that order. Turn the dir/eff level of the reverb down to make it sound more intimate.
5. If your chords don't have enough body in ph production, you can make them bigger by doubling them with another instrument. Even if the part you double it with is extremely quiet (you don't want it to overpower the original chords), it can still add character and definition.
6. You need to ensure that you're properly utilising space in the stereo image when you're creating deep house, and a stereo imaging plug-in can make this a lot easier. Try installing mda image and turning the s width value up to 200% for an extra wide stereo image that'll give your tracks a widescreen feel