I am a member of one writing group and one critique group.
Apparently, this is a little weird, but at my writing group we write. The goal is to get together, encourage each other, work through writing problems together, and write together. We accomplish this by sprinting; we do 20 minutes of writing, and then 20 minutes of talking, in a cycle the whole time we are together.
My critique group is particularly active during on months and particularly ignored during off months. All of the members participate in NaNoWriMo and the associated Camps. Three of the four members also participate in JuNoWriMo. An unofficial offshoot of NaNoWriMo that happens in June. During the month NaNo or Camp is happening we take a break while the members write like crazy. Once the month is over we start back up with our agreed upon submission of ~5k words per week from each member.
As someone who is working towards a full-time professional writing career both of these groups are important. The writing group was a great group to start with, getting to know others in the area who enjoy writing as much as I do and GET the same problems that I talk about. My significant other listens when I talk about my latest writer's block or character motivation problem, but he doesn't write, and can only understand so much. The emotional support of the writers group is amazing, and useful, and real.
The critique group is great for turn around and developing a critical eye. Having a weekly deadline to edit 5k words has been one of the best things I have ever done to improve my writing turn around. Reviewing three pieces of ~5k each week has done wonders for realizing what I can do to improve my own writing. Then there's the actual feedback I receive on my pieces which have been amazing at bringing the pieces up another three levels.
One of the best things I can recommend for a growing writer is finding and participating in both a writing and critique group. They can help bring any writer to the next level.