With such a wide variety of line choice available these days, it's difficult to give advice on what to use as so much is down to personal preference. Here is some of my personnal recommendations.
Firstly - bring a floater, an intermediate and a sinker! As they say in the scouts - "be prepared" (dib, dib, dib!)
At the beginning of the season (up until around mid-April) you will have most success with a sinking line as the fish will typically be lying low due to the lower temperatures. Depending on the height of the water, you may find it easier with an intermediate. The same is true towards the end of the season, although I've also had success on a floater at this time as well!
During the middle of the season - when temperatures rise ro 50 deg F and above - unless we have particularly high water, then a floating line (or a sink tip) will suffice nicely, and in my opinion nothing can beat that bow wave coming straight for your fly and having to hold your nerve until you feel him turn and pull!
We do, however, recommend double taper lines if at all possible. These are very much recommended by the local ghillies and will make your casting and fishing experience so much more enjoyable!
If you would like more tailored advice feel free to "Ask Eddie!"
