from your question it's hard to know whether you're just not focusing right, or whether you just feel your pictures are quite sharp enough.
If you're just not focusing right then I can't help you..
HOWEVER, if you're talking sharpness I've got plenty of advice!
What I'm assuming might be happening with you is that you're finding your pictures are perhaps lacking sharpness.
I've been quite interested in this subject myself, and asked a few question here recently about lens sharpness which I think might explain some stuff, check them out, you might not relate to the questions, but the answers are excellent:
How do you find out the "sweet spot" of a lens?
With all other things equal, in a DSLR, will a larger sensor produce a sharper image?
I used to alway shoot urban landscape stuff with my aperture wide open, simply because I needed the light. The pictures always felt a bit "soft". I've come to understand that sometimes you just need to close that aperture!
Yes, you may need a tripod, or a higher ISO in your case, or in my case a faster film, but especially when your focus is almost at infinity, and you're doing urbanscape/landscape consider upping your f-stop. If you've read my question on the "sweet spot" of a lens, you'll notice the sharpest option seems to be around the upper half of your lens f range.
Generally experiment with your lens around f-11, f-16, see what you think of the results.
Consider the lighting conditions you're shooting in. Usually, if the light is harsh and/or flat, like a sunny day around noon... it's gonna be hard to "perceive" sharpness in your image.
Indeed, sharpness can be a relative thing. You'll notice that during the "golden hour" everything seems to have a sharper edge. This is because this softer, more horizontal light, is giving everything soft shadows, and is actually highlighting the "depth" of subjects. It's like how painters use shadows to give the illusion of 3D. This is true with photography too. It doesn't have to just be the golden hour though, notice night shots look more sharp too because of the quality of the light.
this question might help you too, it helped me! generally, trying experimenting with different light conditions, you'll find some will result in images which feel sharper.
How can one deal with midday light in street photography?