Give them something of value and ask them a question. I ask them a question at the end and it seems to make it harder for them to ignore me.

Contacting them by email is probably the slowest way to get in contact with them. So expect to wait days if not weeks before you get a response, if a response at all. Usually if you just keep it short, use bullet points to point out what it is you want and can do for them the chance that they will reply to you goes up I've seen.