Yes the main thing to remember is that Q codes actually replace whole sentences . . . and merely adding a question mark turns that sentence into a question. Like QRO? Means "Shall I increase power?" Of course they are also widely used on phone, but just as nouns or adjectives . . . Like "I built a little QRP rig". Arguably, there's little advantage, as it takes as long to say "my Location is . . " as "my QTH is . . " . . . but I guess they have become part of our Amateur Radio Jargon. Years ago I saw a whole long list of jargon, that explained to newbies terms like xyl, rig, handle, barefoot, ATU, VFO, PSU, SWL, as well as all the X abbreviations, like Tx, Rx, Wx, Xtal, etc. Then of course there's all the "shorthand" abbreviations used on CW, like cud, pse, wud, rpt, rprt, tks, etc. In the "old days" (when everybody spent years as a listener before getting on the air) you learnt all these just by listening . . . but maybe we should compile a list on here for all the newly-licensed stations?!
I found this list a few years ago. lists abound, like in logbooks etc. I printed this copy off, and it floats around my shack.
When I was in Air Force Mars Transcon CW, we used both Q AND Z signals. http://www.radiotelegraphy.net/zsignals.htm We actually used most of them at one time or another!
CW Help Any one who even considers getting on cw should know at least a dozen common Q signals. There are many, in the big list of Q signals, that just are not useful to our conversations like the ones that pertain to the "heading and speed of your vessel" or "are you taking on fuel", "towing a barge?", ? etc... There are a lot of other common abbreviations used on CW that can shorten a QRS sender's air time from forever to just a long transmission AND, please, Morse newbies, you don't need to spell out your state, use the USPS 2 letter version. Even OH and IA are still shorter than Ohio and Iowa. CA and MA take way too long to spell out, with Morse, on the air.
I usually do spell out the state and other words that I don't want any confusion over. Certainly doesn't take much time unless you are sending very slow.