Get medical self sticking stretch tape (like what they use on an arm after blood is given). I use the medical tape to place around nylon thread to hold the end. You can also place several layers on the tip of your finger as a thimble.
Use Nexcare Tape for your rulers. It is see through, adds texture, and tears easily.
No marking half square triangle. Use blue painters tape. Mark one line right down the middle of the tape and another line 1/4" away on either side for a total of 3 lines. There is a great tutorial on April Rosenthal's blog.