I know it's time to change the wafer when I start to get the itchies or the edge of the wafer starts to peel away from my skin. Most of the time, I can go a week, but sometimes it's sooner. As soon as I change the wafer, the itchies go away.
I like to lay out my supplies and cut the hole in the wafer before removing the old one. Once everything is ready, I remove the wafer with an adhesive remover wipe and take a shower to clean the skin around the stoma. I use Dove soap for sensitive skin.
Once I'm out of the shower, I towel dry the skin around the stoma, put some Calmoseptine Oinment on the skin closest to the stoma, put the Stomahesive paste around the hole in the wafer and apply it to my skin, pressing down for a minute or so to make sure I get a good seal.
I use the Coloplast Assura Extended Wear Wafer (item #2833) with a cloth covered pouch (item #13986). It's a two piece appliance. Since I usually get 7 days wear time with the wafer, I will snap on a new pouch halfway through the week, when the velcro closure shows some wear.
I also keep a cosmetic bag with my supplies handy, so I'm ready in case I ever need it when I'm away from home. I've had an ileostomy for over 3 years and have never had a leak, so I've never had to use the emergency kit. *knock on wood*
Sorry this was so long and detailed, but since you're new to all of this, I wanted to share what has worked so well for me over the years. Also, mint Listerine type mouthwash is an inexpensive and effective pouch deodorizer.
Dx'd Crohn's in '99 at 28. Proctocolectomy and ileostomy in '06.
Disease-free, medicine-free, and very thankful to be healthy again.