Uncapping your bandwidth is illegal, and I strongly recommend that you do NOT do it, but if you do, make sure that you unlock the cap to a certain level as to not raise any red flags. The most legal way to go about increasings your speeds is to replace old splitters on the cable line, reduce the number of splitters in the cable line, removing barrels, replacing the ends on the lines every 7-10 years, and to make sure that the split that you have going to the cable modem has the lowest level of noise, normally 3.5dB.
If you have DSL, there isn't really much that you can do aside from replacing older phones in the house, and by older I mean like phones from the early to mid 90's, which is rare for anyone to have anyway.
Hope that this is helpful...