Ceremony walking down the isle

Like everyone else has said, Tori has got it down! I think the order can be different depending on what kind of religion (if any) the ceremony is being performed under.

Tori is pretty spot on.

My officiant will be just waiting at the front. We have a side entrance so the groom/groomsmen will enter from the side. Then I'm thinking my FFIL will walk in with both my mom and FMIL. My bridesmaids will come in single file (MOH comes in last, just before bride)... My dad is walking me in, and my step dad is joining us at the start of the aisle.

At the end, the bride and groom go first, then it should be the bridal party (paired up or mostly pair up), then the parents. However, the "main entrance" to our ceremony is the side, so I'm thinking my FH and I will leave, then the parents and bridal parties will lead everyone upstairs to the reception.

What Tori said. Minus sometimes depending on the venue. the groom and groomsmen will come out of a side room (more common in some churches).

we are probably having groomsmen come in first. then parents. groom may walk his mom down. then he would be up front after that. then bridesmaids. then ring bearer/flower girl. then me. (my uncle is walking me down the aisle).

As far as I'm aware: the officiant/JOP/Priest should be standing at the alter already, then comes the grooms parents, the brides parents (unless they are walking her down the aisle), groomsmen and bridesmaids (either the men first or pair them all up), the ring bearer with the flower girl, and finally the bride (and parent(s) if planned that way).

As for leaving, I believe it would be the bride and groom together, then the wedding party and parents. Although at the last wedding I went to it was basically once the bride and groom left it went into mingling and everyone dispersing.