I don't know about spring where you are, but here in northeast Pennsylvania it's been slow in coming. And even though nice weather is sure to come, we're expecting the early season to include a lot of high water, cold temperatures, and late hatches. That could all change, of course, but it's looking that way at the moment. We're still getting snow run-off from the mountain and our nights are very cold. With these conditions, it might be wise to make sure the sink-tip lines are in the gear bag and ready to go in case you run into high, cold, water this spring. 
A sink-tip will get the fly down deeper and faster than adding split shot to the leader of a floating line. When the water is deep and the current is moving along at a good pace, the leader and fly will often be swept through before it can get deep enough to reach the fish. If the fish are sitting on the bottom, as they often are in these conditions, you've got to get the fly down to where they are. It won't work if your flies are continually going over their heads. By using a sink-tip the fly line sinks and the leader is pulled down with it. For instance, a RIO 15' Type 3 WF6 Sink Tip has a sink rate of 3" per second. By using a weighted fly like a Super Bugger, the cast will sink quickly and the fly will get in front of the fish. The fish won't want to move quickly in cold water temperatures, so a slow, deliberate retrieve will often produce results. At the end of the retrieves, try wiggling the fly up to the surface before lifting the cast from the water to recast. You might be surprised to find that a fish has followed the fly in and as the fly is wiggling toward the surface, he will often take it here at the last second. If the water is off-color, you may otherwise pull the fly away from the fish that you can't see.
Casting sink tip lines is not difficult if you remember a couple things. Unlike a floating line which is on the surface, a sinking line is — well, sinking. This makes it difficult to recast unless you've stripped in most of the line. A trick that will make it a little easier is to roll cast the sink tip back up to the surface before recasting. Don't give it time to sink again, as soon as it turns over on the roll, pick it up to recast. (Shoot a little line to add to the amount of line you're recasting during the roll if you can.) You will also find that as the amount of sink-tip increases that you are casting, you'll want to slow down the speed of the casting stroke so allow the rod to load. A fairly fast action rod will help with this. You want to be able to feel the rod load but at the same time you want a rod with enough power to keep the line moving without collapsing. A very fast action rod might be good in a strong wind when you're chucking heavy flies, but in general spring conditions, a rod that allows you to feel the cast is best. Since you're not looking for delicate presentations, a shorter leader, maybe 5 or 6 feet, is often all you need. If you find that the leader is landing in a pile upon delivery, keep the rod tip up a couple inches higher on the last cast. This will give the leader time to unroll before landing on the water.
When the fish are sitting on the bottom, you have to go to the bottom to get them. Using a sink-tip line will help make the job easier.
Until next time. -Cathy
We also wanted to share with you that we are putting our Super Bugger Selection on sale for the start of fishing season. For the next month we dropped the price to $24.95 plus shipping so you can replenish your streamer supply. Click here to go to our store site to order.