Google Groups Advanced search in rec.aviation* will be your friend. Some
great posts during the period when Cecil Chapman worked through his
Commercial training.

Part 119.1 know that you're not looking in part 91 for these limitations.

The intricacy's of weight and balance similar to the knowledge test
questions. Load, fly, unload, fly, refuel, load, fly unload, refuel....
what's your weight, where's your CG, what about if you have to hold, when
will you reach bingo fuel and where will your CG be then? Talk to a Bonanza
owner about CG changes with fuel burn.

Spins. Study Rich Stowell's books, charts, and videos. The best I've ever
found to explain exactly what is happening during a spin. Be able to have
an in depth discussion of spins and L/D. Use FAA vernacular directly from
the FAA handbooks. Some DE's insist that in the FAA world, there are NO
other sources of information. Sad.

Required inspections. Get your hands on the log books for your test
airplane. Research all the AD's, know the recurring and single event AD's.
Print them out, put them in a 3 ring binder. Later, when you take your CFI
oral, this will pay huge dividends and save a lot of questioning. Know what
criteria your airplane must meet in order for you to operate it both
privately and commercially. Prove, through the use of the log books, that
the airplane is current and appropriate for the checkride. What about SB's?
Does your airplane need to comply? Why or why not?

Stress, re-stress, and over-stress passenger safety!! Show your DE that
above all you will use good judgment when approached with a commercial ops
proposition.

Understand and be able to explain "holding out". It gets beat to death, but
being able to accurately and completely explain it can be tricky. Use
blatant examples, don't get lead down a path into questionable areas, when
in doubt answer with "if I had any question or reservation what so ever, I'd
defer to someone like you (DE) or the FSDO and if I couldn't I'd refuse the
job". Don't dig yourself into a hole. Remember "favors" towards others
that you benefit by, even if they only secure a relationship with the other
party can and have been considered commercial ops.

Along those lines... don't use any terms that you can not fully explain.
This is a great way to dig yourself into a deep hole. Keep your answers
straight and to the point.

What's the first thing that you do if your landing gear fails to extend?
Fly the airplane. What's the 2nd? Fly the airplane. The 3rd? Relax. The
4th.... get the checklist out. Do NOT on a commercial check ride try to do
anything from memory. The checklist is your ticket. Without it, you WILL
fail.

Talk, talk, talk. Your DE will want to see your knowledge of each maneuver.
Tell him what you and the airplane are doing. Tell him why things aren't
going like they should, tell him what you should be doing and how to do it
and how the airplane will respond. If you do these things, your maneuver
can look like hell, but you've proven your knowledge of the maneuver, which
is what he wants to see.

Systems. Know your airplane's systems inside out and upside down. Talk to
an A&P about your airplane. Read the maintenance manuals. Know how
specific failures effect each system and how to identify those failures.

Minimum equipment lists. Does your airplane have one? Probably not, but
know what you can fly without and what to do if you have inop equipment.
Make SURE everything either works, or is a non-essential item and labeled
inop before your DE discovers it!

Pre flights... what do you check, why do you check it, how do you identify a
discrepancy and how come you're not using a checklist for the preflight?
What happens when you have a larger airplane? Use a checklist. Safety.

FAA Hotbutton issues. Know what the FAA has been hounding DE's about
lately. Runway incursions? Airport Hot Spots? Land and hold short ops?

As you can see, there are many areas to study. The main thing to keep in
the front of your head is that you are asking him to approve your abilities,
knowledge, judgment and decision making on a commercial pilot level. That
means that you want him to tell you that you can work in a position that
entrusts upon you the lives of innocent passengers who have no knowledge of
you or your examiners opinion of you. Those passengers are putting their
faith in you based upon his decision. Safety must be paramount.

Good luck, have fun. The commercial checkride is usually one of the easier
rides. I'm sure you'll do fine. Please let us know how it goes!
Jim