Starting a seam hiding the loose serger thread:
Start your seam holding the loose thread out to the side.
Take the thread and bring it forward.
Cross it over the new seam and serge over it.
Your finished seam should look something like the above picture. A nice finished edge.
Ending a seam and the loose serger thread:
Serge to the end of your stitching line.
Give your thread a little slack by pushing your finger against the two needle threads. You will need this slack for flipping your fabric over. Turn your fabric over (keeping the end as close to the needles as possible) and 180 degrees. You will make your finishing stitches over what you've just stitched. Stitch down a few inches and cut off extra (I still like to tie my extra in a knot).