How to get him to propose?

After 4 years it isn't pushy. Just bring it up in casual conversation. 'So, I've been feeling like I'd like us to start seriously thinking about marriage. What are your thoughts on the subject?' You can talk to him about it. Express your feelings and let him express his. Don't give ultimatums either. I want to be engaged in 6 mos and married in a year is not a good way to start out the convo. As long as you don't nag him about it everyday, its fine. :)

Just be honest and have a nice talk with him. four years is plenty of time, you need to find out what he is waiting on.

Being together 4 years is meaningless if you can't communicate with him openly, honestly, and at a mature adult level. This is your future, too, and if you truly can't think of a way to discuss it with him, this should concern you a lot more than the fact that your guy seems to be stalling.

Write your feeling on a paper and send that letter along with flowers. I think its a great and sweet idea.

Unfortunately, you can't make him propose, and if you do you'll never be sure that he did it for the right reasons. However, four years into the relationship, you have a right to know a general timeline. Just have a good talk about what you both want to accomplish personally and professionally, and where you see marriage fitting in. See if you have similar ideas; and, if not, is there a compromise that works for both of you? After you have this established, just try to be patient and enjoy what you have now. It'll come eventually. :)

throw out little hints here and there and see how he responds to them. when he is ready, he will ask. if that doesn't work then the only thing left to do is be flat out honest with him.