Demonstrate that you've tried to help yourself. Briefly explain what you've tried independently so they know you've tried to solve your problem for yourself before.
Demonstrate that you've acted on the person's advice previously so they won’t be weary you might be wasting their time and not following through.
Consider the timing of your request and asked them when they are free to help so you’re not inconveniencing others.
Use the "Foot in the Door" or "The Door in the Face." In the former a small request that gets the person into "yes" mode is followed by a larger request, while in the latter a large request is denied and followed by a smaller request, which seems more reasonable due to the earlier unreasonable request.
Don't make someone guess what you want, be precise.
Make your requests using multiple channels in customer-service situations. If you don't succeed at first, hang up and try again with a different representative, or switch to a different customer-service channel.
Offer or give more help than you ask for to make people more receptive to your requests.