One, don't let anyone tell you that you HAVE to be a FAC, or even that most do. If you don't want to and you're in the half of your peer group that is regarded as not sucking, you probably won't be forced into a FAC job (not to malign anyone who rocks and got drafted--I'm just speaking to my experience in my squadron). That said, I chose not to do it, and I kind of regret it, mostly because I think I've missed out on learning more of the big-picture "MAGTFery" stuff I used to mock in my younger days. As long as people are talking about good FAC deals, I've known 3 guys who FACed in 2nd Tank Bn and said it was the best thing since pop-top beer cans.
That said, being what is called a "team player" by some, or as "taking it in the shorts" by others, is a good way to get what you want later. Often by filling a job the monitor has a hard time filling, you'll get a better deal on the backside. A lot of guys took an unwanted FAC job and got the orders to be an IP they wanted on the other side. Others do the FAC thing and want to go right back to a fleet squadron. There is not schedule set in stone, but there are what are called "left and right lateral limits" that you figure out as you go. For example, going from your first fleet tour to a FAC tour to FRS instructor is firmly in the straight and narrow. Going from the fleet to be a SAR pilot to the fleet is touching the left boundary and coming back again. Going from the fleet to grad school is going completely outside the lines and you'd better get back inside if you want to stay for a career.
Take it for what you will though. I've been on flight orders for nearly 14 years and have a letter in my OMPF from the Deputy Commandant for Aviation stating that no one should judge me for deviating from a normal career path, but that's another story.