"Make it easy for them to give you what you want"

There's a lot of ways to interpret that, and most of them help. For instance, if you're asking your boss for a raise, if you just say "Hey boss, gimme a raise" you're making it hard for them. If you say "I think I deserve a raise, here are multiple, documented, examples of where I've helped increase revenue/fix a problem that could have cost us/improved customer retention/etc" then you're making it easier for them because they have a list of positives to justify it.

Generally if you're asking a question you need an answer to, or for something in particular, spend a little time thinking about the request from the other person's point of view. What do they need to be able, and inclined, to help you? When you know that, make sure you supply it.

I've found it to be a powerful way of approaching discussions, and it can make a lot of situations make more sense when you realize one party didn't do it and didn't get what they want.

Sometimes, of course, making it easy to give you what you want just means making any other outcome harder instead. >:)