A small announcment: I am no longer an attender (or semiquaker as I tended to refer to it) but an official member of the Hampshire and the Islands Area Quaker Meeting and consequently the Religious Society of Friends. I started attending Quaker meetings in January 1997, but only decided to become a member last September. I had been pondering it for a couple of years, but there's no urgency to joining since there are hardly any demarcations between attenders and members. Asking for membership is just making a public commitment to the society.
On the way to becoming a member, it's advised that you attend the local business meetings and take part in the running of the Society, and in my case I'm an assistant treasurer. Also you should read some of the Quaker literature and go along to talks and discussion groups. Very wisely they also suggest you visit other Quaker meetings so that you don't decide to join just because you like the people in your local meeting! Then you make a formal request to the membership co-ordinator for your Area Meeting and two Members (one from your Local meeting, and one from elsewhere in the Area) come to visit you, and you have a very informal chat about the Society to make sure you understand the different aspects of Quakerism. They then write a report which is submitted to the Monthly Meeting for the Area, and hopefully at that point you're accepted as member. In a nice piece of serendipity the Monthly Meeting where I was accepted was on my birthday - March 14th.
I don't think you'll see any obvious difference in this journal, although you may find the Quaker Jargon Buster handy! I don't feel much different in myself, although I'm happy with the decision. It was very strange when I was on holiday though, and we were having a casual discussion about religion, and I said "I'm a Quaker." I had the urge to turn round and see who that was speaking :-)
I'll finish off with the quote that prompted my decision back in September.
26.39 True faith is not assurance, but the readiness to go forward experimentally, without assurance. It is a sensitivity to things not yet known. Quakerism should not claim to be a religion of certainty, but a religion of uncertainty; it is this which gives us our special affinity to the world of science. For what we apprehend of truth is limited and partial, and experience may set it all in a new light; if we too easily satisfy our urge for security by claiming that we have found certainty, we shall no longer be sensitive to new experiences of truth. For who seeks that which he believes that he has found? Who explores a territory which he claims already to know? Charles F Carter, 1971