I'm sure there are different models. Mine's one of the Foodsaver ones. There could be some differences in different brands and models, so bear that in mind when you read what I say.
You have different options as to which bags you use. You can get different width pre-formed bags or just rolls that you cut to length. I'd suggest you start with the bags to get a feel for it, but now I practically always buy the narrower rolls and make my own. Part of that is what you are sealing though. You may need the wider ones.
If you make your own bags, don't try to get the length too close. It takes a fair amount of space to reach into the vacuum area. I used to try to measure it really close but have since just decided to make sure I don't have to throw the bag away because I cut it too short. You learn as you go.
Those things don't handle wet or damp food very well. The suction will draw out whatever moisture there is in it and moisture where it seals prevents it from sealing. I get around that by filling the bag with the produce and freezing it in the bag before I make the final seal if the produce is "moist". When I do that, I only take one or two bags out of the freezer at a time so they don't thaw while I'm working on the others. I use a dry cloth and wipe the inside of the bag to remove any ice crystals or moisture where it is going to be sealed.
If there is any question if it is sealed, just seal it a second time. Mine has different ways if sealing, one with suction and one without. For a second seal, I use the one without suction.
Think about how it is going to be used when deciding what sizes you are freezing. I freeze some stuff in serving sized portions, Some I freeze in bulk.
If you freeze something damp, you can't break it apart if you only want a little of it. I'll use chopped onions as an example, but this method could be used for a lot of things. When my home grown onions get toward the end of their storage life, I chop them and tray freeze them. That means I put them on a cookie sheet on wax paper and freeze them, busting them up a couple of times during the freezing time to keep them from sticking together. Then I pour them in the bag and freeze them. When I need more onions, I open a bag, use what I need, and keep the rest in a ziploc type bag. Since I use one of these ziploc bags in a few weeks, they don't get freezer burn before they are used up. The vacuum bags work real well to prevent freezer burn. Since they were tray frozen, I can measure out how many I actually need.
A lot of this stuff becomes clearer when you actually try to do it. The vacuum sealers are not that hard to use.
