Announce your intention to complete all phases of treatment as efficiently as possible:
You don't want to be mired in a black hole of counseling year after year, no matter how much time you have on probation. Your ultimate goal in counseling, besides not reoffending of course, should be to graduate to a maintenance program. Ask the counselor how long one should expect to spend in the first phases of treatment before being eligible for a maintenance program.
Relationship and socializing with other group members:
The group I attended allowed members to socialize outside of the counseling session, while others groups are more strict in their policy and prohibit such contact. It's completely normal for guys to form strong bonds in treatment groups and want to socialize and help each other outside the group setting. I gave my phone number to other group members for support in the event they were not well, engaging in problematic activities, or needed a ride to group. One good example of how this can work was an instance I was asked by a fellow group members if I would help him disable his computer since he was cracking out looking at adult porn, knowing it would lead him to seeking out illicit websites and chat (this guy was in maintenance and was not in violation of any condition or restriction). That's not necessarily something you ask your neighbor to do or want to explain why! Whether you engage other offenders outside the group or not, it is something of a personal choice. You have to be certain can remain objective and still, for instance, call this person out in group the same way you would had you not been hanging outside the group.
Ex-cons versus those who didn't do time:
There is an inexorable bond and with guys who've done time behind bars that can sometimes border on resentment toward others in the group who weren't sentenced to incarceration but just probation or those who are convicted but don't have to register as a sex offender. Predictably, a offender who had money to spend on a good lawyer to get a more desirable outcome with sentencing or had connections to achieve the same aren't celebrated in group.
In fact, there's a convoluted mixture of feelings to deal with. Ex-cons (me included) recognize within each other the pain and suffering we had to go through inside prison. Now being out, we may overtly reminisce and half-heartedly joke about the trauma and madness of prison. Think of it - and I am not equating here - like veteran soldiers looking back at their recent war experience. Even if one soldier wasn't laying next to another in a ditch fighting for their lives, they would have an implicit understanding and camaraderie that civilians could never have. Same goes with ex-cons: You don't understand. You had it easy. It was 'Nam, you weren't there, man! You get the idea. You'll have to excuse the ex-cons in the group if we go off on a tangent involving prison, get pissed and resentful, and leave others out of the conversation. We've been to our own hell and back and survived to varying degrees. It's not a feeling of "we are better than you", more a mixture of feelings of unfairness, pride, and camaraderie that is undeniable. If you were never incarcerated, don't take this personally in any way. Besides, having avoided prison is something to be very grateful for! Trust me, being an ex-con is not a club you would have wanted to be a part of and all of us ex-cons would much rather have stayed on the outside.
However, even among ex-cons in group therapy, there's something of a hierarchy of who did how much time, at what facilities, federal/state/county bid, etc...typically with the most "respect" going to the guy who had the hardest/most time. Kind of crazy, but prison does follow you to the outside to some extent.
Speaking of hierarchy, there may also be an unspoken hierarchical structure to the group you join that will never be spoken about very much. This is not really obvious and is more of a perception carried by and colored with society's norms and values. A good counselor will make sure everyone in the group, regardless of their crime and/or age of victim(s), is equal to one another and no one tries to show moral authority over another.
It is human nature to make yourself as least heinous as possible, especially among other offenders. In prison, the guys who were in on statutory rape got a different reception than those in on child rape (what, was your victim twelveteen?!). This can extend into the treatment group. Nobody wants to feel like "the worst of the worst". It's a coping mechanism many offenders adopt to varying degrees: at least my victim was and adult; at least my victim was in his mid-teens, reached puberty, and was willing and I didn't force him; at least my victim was someone I knew and cared about and not a snatch-and-grab; at least I didn't penetrate him like he did; at least she wasn't my own daughter; at least he wasn't a toddler; at least I only looked at kiddie porn and didn't ever touch a child etc...
Truthfully, we all engage in this minimizing and coping at some level. Your ego really doesn't want to be the biggest pervert in the room. It's a protective mechanism that has its function. Just keep in mind this ranking of other group members may rear its head in some comments in various ways because, and let's be frank, American society views sex with a 15 year-old girl much differently than sex with an 11 year-old boy. Sex with a 15 year-old female is more "acceptable" than with a 11 year old male and just because someone is a sex offender doesn't mean he is not homophobic.
So no matter your conviction, don't feel like you can walk in and feel like the top dog or the biggest freak in the room.