I just use the "old" method: if you're more-or-less 6 ft tall, your arms
outstretched is about 1 fathom (6ft). Pull the line out that way and
count. OTOH, markers ARE nice - even electrical tape every 20 ft or so.

Somebody mentioned whipping cord. I might give that a shot since it comes in
teal (my boat is teal, forgive me my vanities but even my cutlery matches
.... sorry).

To see if you're really "hooked" while backing, look at the trees beside
you. If they appear to be moving forwards, you're still moving backwards.
Line up a couple, and when they don't move wrt each other, you're stopped.

For the first time this past weekend I increased the engine above idle speed
after the initial set. I didn't really have the guts to do that up until now
and it worked great.

I think I'm getting a somewhat better sense of the feel of the boat. This
time when backing down I felt the anchor chatter a bit and then bite. I
could feel the boat come to a stop and noticed its change in attitude as it
tugged the line. When I increased the throttle adding a couple hundred rpm I
could actually feel the anchor dig in further and then the bow nosed down.

I had no doubt this time, it was set.

By the time we left the anchorage we had swung through about 150 degrees and
in fact were pulling the anchor up from almost the opposite way we had set
it but it was still dug in tight. This was the first time I needed the winch
to free it (windlass whatever ... geez so many terms) and the mud was packed
in so well I had to finish cleaning it back at the marina (as opposed to
just dunking it a few times).

Again, Peggy's recommendation: http://www.snake-river.org/ Accugage tank
sensors, the cheapy one shows empty, 1/4, 1/2, 3/4 and full for 4 tanks.
Seems to work great!

I seem to remember this being mentioned before. I checked the site out and
I'll be asking some questions before my purchase. Thanks.