<p>I can think of in 4 options, which #1 and #2 are the best ones. They are:</p>

<ol>
<li><p>If the question was not already edited after it was put 'on hold'; edit it for clarification (if you are positive you know how), so it can be automatically sent to the reopen queue for peer review. However, a caveat is that in many occasions only OP will be able to edit the question to address the close reason (don't edit in this case; wait for OP to step in).</p></li>
<li><p>Reach 3k reputation and earn <a href="https://stats.stackexchange.com/help/privileges/close-questions">cast close/reopen vote privilege</a>, so to cast a reopen vote and send the question to the reopen queue for peer review. Leaving a comment explaining why you think the question should be reopened, might increase chances of it being reopened.</p></li>
<li><p>Flag it for moderator attention and explain your reasons, tell you want to post an answer; but unless it is very good reason <a href="https://stats.meta.stackexchange.com/questions/4689/is-there-a-procedure-to-propose-the-reopening-of-a-question#comment12834_4689">it won't work</a>.</p></li>
<li><p>Ask for help in CV Meta (kind of what you did with this post).</p></li>
</ol>

<p>In my opinion #4 competes with #3. However, #1 or #2 should always be tried first, and in case of negative results, see if any new piece of information was added (e.g.: edits to question or new comments from peers), then evaluate if #3 or #4 are worthy a shot.</p>
