Tack sharp photos are a photographers dream! Here are a few tips to get them:
1. Always use a tripod, even if you think you don't need to. 2. Use a cable release so you don't have to actually touch your camera when taking the photo. If you don't have a release then use the timer function. 3. Use Mirror Lock-Up 4. Get close! The closer you are the less the aberrations in the air will affect your photo. 5. Use Photoshop!
These are the things I do. I don't always take tack sharp photos, but it's usually because I neglect one or more of the tips above.