Ok, this is advice from my days on the "other side of the microphone". Yes, they may have assigned left downwind, but when there's a bunch of planes, sometimes they need all the help they can get.

That first bit of help is not "stepping" all over everbody (more than one person talking on frequency at the same time). No matter how hard you try, it will happen with the current generation radios (the next gen radios will have ATC override).

Second, of course, keep it brief. Tell 'em "important" info every time, even if you think they "should" know it.

So, I'd suggest, "Cessna 123, midfield, left downwind, Rwy 24, option". You can leave off the "Trenton Tower", because you've already established radio communication on your initial call when you told them you had the ATIS inbound.

The same goes for headings, speed assignments, etc. "Podund Tower, Cessna 123, ten east for full stop / option / Touch and Go / Overhead / straight in, ATIS Romeo", then add the "250 knots assigned" if appropriate (or heading 360 assigned, or traffic in sight, following the yellow Belchcraft, etc).

If it's an absolutely cold call, meaning that tower never heard of you, say, in the last 10 minutes, particularly if its busy, make that initial call extremely brief. "Podunk Tower, Cessna 123" and let ATC reply, or you might add "with Romeo" or "10 east", but that's about it.

You'll learn that every tower has it's own local procedures, which, with experience, will help you tailor your calls. But the basics are always the same.

Brief, clear, steady speech rate is probably the MOST fundamental. You'd be amazed how many experienced aviators and controllers alike speak so fast, monotone, too much info at once, etc, that the only response is "say again".