You should /never/ have reception problems when you subscribe to cable. That's the whole point of subscribing, to have the signal brought to your door for you.
If you're asking whether its possible to get better picture quality, these are the things to consider:
o Your cable company compresses its signal so much that picture quality is compromised, at least a little. Some TVs do not handle a highly-compressed signal well. The level of compression also depends on the cable company. I believe rural cable distribution tends to be more compressed than urban. If you want the highest-quality signal then hook up an Over-The-Air antenna and your picture quality should improve markedly. Of course you will receive fewer channels if you go this route, and must be within a reasonable range of the broadcasting antennas in your area.
o Just because you have a HD TV doesn't mean the signal that you receive is High-Def. I believe the majority of signals are still Standard-Def (but broadcast in a digital format). There is next to nothing you can do that would convert a Standard-Def signal to High-Def. I believe there are up-converters but they will not be inexpensive and I haven't run across one myself, so I can't vouch for their efficacy. There is no way, however, that a an up-converter can add the same amount of detail found in High-Def signals.
o You may want to look through your owners manual and try changing the number of lines that your TV scans horizontally across the screen. The picture quality could be affected by this setting. For example, the highest quality High-Def setting is 1080p. Some of the lower settings are 1080i and 720p.