I've developed a thing for snow globes about a year ago, and decided to make some of my own. It's a pretty straightforward project - all you need is a jar with a lid, small items to fit inside and a bottle of the Best Glue Ever.
Having said that, there are a few things you need to consider. First is the size of your jar. You want to make sure your items aren't too big to fit inside. Case in point: the glass jar I used has a dip in the center (which I didn't notice until I'd already glued my larger tree).
The second is the depth of the lid. The lid on this jar was quite deep, which affected how the items would look in the jar. If you place your items directly on the lid bottom, they can look strange. I decided to raise the "bottom" by adding layers of cardboard so that the bottom of my scene would be even with the top of the lid.
Once the cardboard circle was the right size I took more pieces of the mailing box and cut a series of squares. These were to be glued to the bottom of the lid first.
I made sure the squares were smaller than my circle, then snipped the corners just to make sure I wasn't going to have any problems putting on the lid. I used the Best Glue Ever to adhere the cardboard to the metal and each subsequent piece of cardboard.
Here's my stack of cardboard. If you don't have cardboard you could use anything you have on hand to raise the bottom -- chipboard, plastic bottle caps, cork, or thick foam.
And after layering the square pieces I added my circular top piece. This last piece is almost as high as the lid. You can see how much smaller my raised bottom is than the edge of the lid to accomodate the thickness of the glass jar.
The next step is to dry-fit and arrange your pieces. Add a couple things, place the jar on top, make some changes, etc. I tried several sizes of trees and considered using this red bow and some bells, but decided the scale was too big for this deer.
Once you're satisfied, glue everything down with more of the Best Glue Ever, being careful to make sure your items stay inside the circle. After I glued my trees and deer I added a layer of glue to the bottom before adding some tiny styrofoam balls. I was hoping they'd look snow-like, but again, the scale was a bit too big. No worries, I grabbed my container of Sparkly Fluff and used a bit more of the Best Glue Ever to coat the styrofoam.
It's a bit hard to photograph well inside of the jar, but the Sparkly Fluff covered balls ended up giving me a lot of dimension, as if the deer was standing outside after a snowstorm.