Since glass is relatively inexpensive to make there are all kinds of antique glassware. It can be overwhelming to start the identification process if you have a piece you'd like to know about. I recently took a dive down the glass-identification rabbit hole after picking up a dish at a yard sale that intrigued me-- here are a few tips to get you started.
This starting point should go without saying. If you have markings on your piece, you've already got a great head start in learning about the history of your item. Google it up and see what you can find!
Cut vs Pressed Glass
Pressed glass means the glass was made over a mold, which leaves a seam. Some of the upper end pieces have hard-to-find seams, but if it's pressed glass there's one there somewhere. Pressed glass is fairly common and comes in a variety of patterns, colors, and shapes.
Cut glass (aka American Cut Glass) is glass that has been softened by the addition of lead oxide. You probably know it better by its common name-- crystal (any glass with lead is considered crystal). Cut glass is usually more valuable and will appear more translucent than pressed glass- it will also disperse light into color when examined.
A super easy way to determine if your glass is cut or pressed is to find a groove and gently run your finger over it. If it's smooth, you've got pressed glass. If it feels sharp (like it could cut you...), it's cut glass.
A quick way to know if your glass item is handblown is to flip it over and rub your thumb over the bottom. If it's flat and smooth, it's not hand blown. If it is, there will be a bump-- maybe polished or worn, but still there-- where the blow rod was used to create the item.
A great resource for pattern identification can be found here. This is the most comprehensive cataloguing of patterns I have found online that doesn't charge for a subscription to use.
Other Starting Points
Make note of the size, color, shape, and type of piece you have. Use these details as online keywords to search with. Your vase might actually be an antique banana holder or the bowl you're using might be a compote.... learning more about your item is probably only a photo or a few keywords away on the internet.
Lastly, if you have Google Lens this can be the easiest, fastest way to get to the bottom of things. Simply snap a picture of your item and select "Images" in the results. Scroll around and you may find comps or your exact item in the photos it provides.