Don't Ask to DM
Every now and then, in online chat rooms I hang around in, someone pops in and says something in the lines of,
Foobar123:
This is bad form, for several reasons. What the person is actually asking here is,
Foobar123:
There are plenty of reasons why people who CAN HELP would not admit to it. By asking, you're asking for more than what you think you're asking.
You're asking people to take responsibility. You're questioning people's confidence in their abilities. You're also unnecessarily walling other people out. I often answer questions related to languages or libraries I have never used, because the answers are (in a programmer kind of way) common sense. The last thing you want is to miss out on potentially valuable help simply because a user is not comfortable in the social situation you have made a pre-requisite for providing it.
Alternatively, it can be seen as..
Foobar123:
..which is just lazy. If you're not willing to do the work to solve your problem, why should we?
The solution is not to demand promised help in advance, but just to ask. Someone who is idling on the channel and only every now and then glances at what's going on is unlikely to answer to your "can someone DM me" question, but your actual problem description may pique their interest and get them to answer.
So to summarize, don't ask, "Can someone DM me?" but rather ask, "Hey where can I get help with [problem] and [other relevant info]?"
Other similar problems:
Don't Ask to Ask,
The XY Problem,
No Hello.
Further reading:
How do I ask a good question?,
or if you have more time:
How To Ask Questions The Smart Way.