Hi! I was wondering the same thing, and though my findings were not entirely conclusive, I might be able to help with resources.
It's difficult for me to understand the situation in which this form of the verb should be used, but I was able to find very many exemplary sentences.
On the website jisho.org, they have a Sentences feature, but sometimes it takes a little bit of "hacking" to get the results you want as they will only yield results containing exactly the characters you entered as they were input.
Because your question concerns the use of 置く (to do in preparation) following a ~te form verb, you can input 「ておき」into the sentences tab and it will yield about 7 pages of results (using て置き will yield different results but a considerably smaller amount). Though technically you're searching the entire database for anything that literally contains "teoki," there really isn't anything else that isn't "~te-verb + oki" in this context.
Likewise, you can search sentences that use different tenses of the verb by literally typing:
ておい ー past tense (as in ~ておいた)
ておか ー negative form (〜ておかない/〜ておかなかった)
ておく ー simple form
or in your case ておきた ー to want to do (~ておきたい/〜ておきたかった/〜ておきたくない etc...)
I was able to read sentences upon sentences in this way and improve general understanding of the use, even though I still couldn't translate into English the exact reason for it's use... Anyway, I hope I was able to help at least a little bit, and that you don't find this entirely useless. It would be great if someone else could perhaps clarify the difference in saying something like 教室をきれいにしておきなさい vs 教室をきれいにしなさい。
When is it appropriate or inappropriate to use?
て + おく is (according to Tae Kim's guide) makes a verb done for the future (like 晩御飯を作っておく), so 伝えておきたかった would be "wanted to convey/report for the future".
Hi! I was wondering the same thing, and though my findings were not entirely conclusive, I might be able to help with resources.
I think 伝えておきたかった means: 'wanted to tell/report/convey [to someone] [something] (before it actually happened--but now it has already happened)'.
Thanks everybody that makes sense, for a split of second I thought it was て＋おきる and I didn't get it.