One of the most common bad habits I see new fly anglers have when stripping a fly is keeping the rod tip too high off the water. When fishing still waters such as lakes, it's important to maintain close contact with your fly so you can strip efficiently while detecting and reacting to strikes quickly. It will help you manipulate the fly better and catch more fish!
A high rod tip means there can be excess loose line between the tip and water's surface. If a fish bites, you may not feel it immediately since you don't have a straight, direct connection to the fly. To remedy this, try keeping the rod tip angled downward so it's just barely above the surface of the water. If using a full sinking line, you can even stick your rod tip slightly underwater if you prefer which can also keep your fly deeper, longer. Holding the rod tip low not only lets you feel strikes faster, but wind won't blow a big bow in your line, you'll strip more precisely, and the rod tip won't "bounce" or flex when you strip the line. You'll also be instantly in position for a strip-set or to set the hook via the rod with a nice long range-of-motion.
Keeping the tip close to the water not only helps when actively stripping a fly, but can also be of assistance when preparing for another cast. If the rod tip is up high, any loose line between the tip and water can make for an awkward transition when you go to start a new cast. On the other hand, if you're ready to recast and the tip is low with no loose line dangling off the rod tip, everything is nice and taut and you'll be able to smoothly transition into an efficient and full casting motion.