While I'm not married, I have been engaged twice and proposed to a total of 3 times.
The first engagement was over the phone. My b/f and I had been living together for a couple of years and he was in sales and travelled. One day he called me from where he was and during our conversation he asked me to marry him.
I said yes. Never had a ring. We just knew we were going to be married.
We had a date scheduled for the following March, and I had some planning done, not much. But on Halloween he was out of town again, and I had been thinking long and hard about my decision. See he was very mean and cruel, not only physically, but emotionally and mentally and psychologically. Plus he was a compulsive liar. I finally woke up and realised that I didn't want to be married to him for the rest of my life and that I deserved better. So I broke up with him the same way he proposed...over the telephone. Only by that time our phone had been disconnected (it was in his name) because he hadn't paid the phone bill. I had a new phone connected under my name, but didn't give him the number, instead I called him from a pay phone at 7-11
The second time I was engaged I had a ring but no date. Again it was an informal proposal. I was at my b/f's house and he said something about "we should get married", I said "You think so?" and he said "yeah". I said "Ok"
I didn't want a fancy expensive ring, so we went to a local pawn shop and found something smaller and cheap. I still have it. When we broke up I wanted to return it, but he didn't want it back. I don't wear it mainly because my fingers are too fat for it, but once I lose weight and it fits again, I'll wear it on an alternate finger.
The third proposal was from a guy I had been seeing for a couple years. He was separated but not divorced. His "ex" wife lived in another Province with a guy, but they hadn't gotten divorced because neither one wanted to be the one to initiate the divorce proceedings or pay the expense of a divorce! Anyway, he asked me to marry him one day while I was at his house. I told him no because he was not free to ask me that seeing that he was still technically married even though their relationship had ended some 5 years earlier and she had been living in another province for 3 of those years. So he asked me to move in with him and again I said no, for the same reason. We broke up not long after that. And I'm really glad that I hadn't uprooted myself and given up my apartment to move in with him.
I don't think a proposal has to be planned and formal. So long as the 2 of you love each other, even a quiet understanding that you are getting married is enough IMHO.