If you are anything like me when I got my new ostomy a year ago (happy anniversary to me and my pal!), you are terribly confused about all the products available and what to do with them in spite of all the information and samples the ostomy nurse handed to you. I hope I can pass on to you some un-confusion about the whole thing.
First, think of the whole thing like a beautiful layer cake rising in all its glory from the cake plate of your skin. Notice I didn't say your stoma, because we all know the one thing we do not lay anything on top of is the stoma itself. First, consider the condition of your cake plate - your skin. Is it cracked and chipped? Is your skin red and weeping, perhaps with sores? Is it just irritated and itching? Or is it in good shape? If your skin has sores, your doctor may have given you some specific cream or ointment to put on to help it heal. You also may need to cover the sore before putting any further layers on, because the adhesive in your appliance is almost sure to further irritate the sore. If your skin is weeping, but without open sores, you can use stoma powder to absorb the moisture and help soothe the irritated skin. Follow with a barrier spray to hold the powder in place and keep the adhesive on the appliance from further irritating the skin. A barrier spray (or wipe - there are a number of different products which do the same thing) can also keep waste away from the skin - the number 1 cause of skin irritation. If you have good healthy skin around the stoma, and you don't have any problems with skin irritation, you can skip this layer.
Next, is your cake plate perfecly flat? Is your skin smooth and even around the stoma, or does it have hills and valleys which can cause an appliance to leave gaps when placed on the skin? If you have hilly terrain around your stoma, then perhaps stoma paste is just what you need to fill in the gaps and provide a smooth surface for the appliance to lay flat. Note that when you apply stoma paste, you are reducing the area where the appliance adhesive hits your skin - in spite of its name, stoma paste is NOT an adhesive or glue! It merely fills the gaps to even out the surface and block any wastes from breaking through by traveling along a gap between the appliance and the skin.
An alternative to the paste is a flexible barrier ring, like the Eakin seals. These are moldable so they fill the gaps and valleys in the skin around the stoma, and also provide a surface to which the adhesive of the appliance will cling tightly, unlike paste. The only drawback I have ever found in these types of barrier rings is that they are fairly thick (not a whole lot, but somewhat, in comparison with barrier spray). This may not be of any concern, unless you have a jolly St. Nick tummy, or a lovely poking-out peristomal hernia. Start adding in additional layers and you start to look as if you were about 3 months pregnant! (maybe not an issue for women, but men? ...) There are very thin barrier seals, like Stoma Seal which will work quite well if your hills and valleys are not very pronounced. Not only is it water-proof and waste-proof, but it also provides an excellent sealing surface for the adhesive of the appliance.
Once your skin is prepared, you are ready for the next layer. In a 2-piece system, this would be the faceplate or wafer. In a 1-piece system, this would be the whole appliance itself. I will mainly discuss the 2-piece system, since that is the type that I use. I just don't know enough about 1-piece systems to discuss them intelligently. (Maybe someone else could step up to bat and talk about those?) In a 2-piece system, the faceplate is placed on the prepared skin separately from the pouch itself. There are faceplates available with precut holes in the center to fit around the stoma. However, if your stoma is not exactly round or evenly oval, then the pre-cut holes will not fit properly and you will need to use faceplates that you can cut your own hole in to properly fit your stoma. Also, a new stoma will continue to shrink and adjust its size and shape for a few weeks. So in the beginning and for some time, you will need to measure your stoma and cut to fit each time you change the faceplate. Once it stabilizes, you can use one of the plastic backing plates from a previously cut-to-fit faceplate as a template which specifically matches YOUR stoma, making it MUCH easier to change the faceplate each time.
Once your faceplate is in place, you may want to consider a water-proof cover for your faceplate. The Aqua Seal and SureSeal are 2 brands which are extremely thin (like plastic wrap) and which go over the faceplate (tucking around under the flange) and reach beyond the edge of the faceplate. There are also thicker barrier strips which go around the faceplate and extend beyond the edge of the faceplate. All these products provide additional security for the edge of the faceplate to prevent the faceplate edge from rolling up or coming detached from the skin. In addition, the Aqua Seal and SureSeal completely cover the faceplate and make swimming, bathing and even hot tubs enjoyable without worrying that your faceplate will detach (how embarrassing!). Anything to boost your confidence and go back to enjoying pre-stoma activities! Note that all these products can also be used with 1-piece appliances, as the pouch tucks through the center hole and flattens to the outside of the water-proof cover.
Lastly, the pouch is snapped to the faceplate, and your cake is complete! There are lots of different attachment systems, from stick-in-place adhesive types to flanged locking systems. I personally prefer a pouch that snaps into place with a positive attachment system that you can definitely tell is properly and completely sealed (but then, I've always been a bit paranoid!). Here again, once you decide on an attachment system, there are all kinds of pouch designs! When you were in the hospital, you probably were fitted with a pouch with a re-sealable end which can be emptied without removing the pouch, and used for several days. You can continue with that design if you wish, or you can choose a sealed pouch which is a totally disposable single-use design. There are advantages to both types - the re-closable pouch is more economic, but more time-consuming and labor-intensive to use. There can be unintentional splash-back when emptying the pouch in a public restroom. On the other hand, the closed pouch is easy to use: remove, clean around the stoma, snap a new pouch in place, and dispose of the old pouch in a plastic waste bag and toss into the trash - even in a public restroom. The drawback is obvious - you use 2-4 pouches per day, rather than 1 pouch in 2-4 days. If you have to pay for your own supplies, that may tilt in favor of the re-sealable pouches; if you are covered by insurance, that may make the ease of use of the closed pouches much more favorable. As far as size goes, most resealable pouches are longer than closed ones, simply because of the additional length needed for the closure. Closed pouches come in a longer 9" length and a shorter 7" length (for all you shorties out there). At only 5'2" tall, I prefer the shorter 7" length because it doesn't have to be guided down my pants leg (very uncomfortable!) and it just fits under all my clothes better. Again, this is a matter of choice.
If you need more security for your pouch, some pouches have tabs which connect to a belt which goes around the waistline and holds the pouch securely and prevents it from popping off at an inconvenient time (is there ever a convenient time?). In addition, if you have a peristomal hernia, there are wider belts which do not connect directly to the pouch but instead have a hole which the pouch passes through. The belt closes with velcro to make an exact fit, does not put any pressure on the pouch or the stoma itself, and helps support and reduce the size of the hernia. If the pouch is the icing on the cake, I guess the belt would be the candles! Not always needed, but nice on your birthday!
Good luck to all the newbies and remember - build your cake carefully and enjoy life all day!