There are a variety of interfaces that enable you to program drums, including virtual drum machines, external hardware drum machines and the "Piano Roll" interface that is found in most commercially available digital audio workstations. The most intuitive interface is the step sequencer. It is based on a grid visual, the vertical axis represents the instruments in the drum kit and the horizontal axis represents time, in beats and bars. You plot the drum strikes by clicking in a grid square to turn it on.
For a more natural groove, you may wish to play in the beat or add accents in real-time, as the backing groove plays back. Normally this calls for an external device, such as electronic drum pads or a MIDI controller. However, some programs, including Apple Logic and Acoustica Mixcraft let you use your computer keyboard as a MIDI input device. In Logic, click "Window" and select "Musical Typing." In Mixcraft, click "Help" and select "Musical Typing Keyboard." You can now use your computer keys to input drum beats.
A click-track, or click, is essentially a digital metronome. Without a click, you can't hear the tempo of the song. Clicks are useful as a timing and structure reference. You can customize the click to suit a particular application. For example, add an accent on the first beat of a bar so you know which drum notes to hit harder. A click also serves as a count-in reference for other musicians playing on the track.
Since MIDI contains only data, you can change the sound, feel, volume and pitch of a MIDI note after recording. In terms of recording, this means you can record a groove and then change the drum-kit sounds. To get the best groove, program with a basic kit sound with minimal effects. This way you can hear the groove in its pure form, without influence from sound effects. Once you're happy with the groove, you can edit the sounds to your preference.
To give yourself greater scope for mixing and post-production effects, record each individual drum part separately. This way you can apply effects individually, rather than to the collective drum sound.
Typical sequencers and MIDI programs have a tool that slightly alters the MIDI note velocity and placement, to emulate the feel of a real drummer. No drummer is as tight as a computer, so the humanize tool makes the computer less refined.