Examine the table from all sides, including turning the piece over and looking at the bottom and looking inside any drawers. Handmade pieces might have a mark from the maker that identifies when the piece was crafted. If it's a mass-produced piece and you find the maker's label on the furniture, then contact the maker and ask about its age.
Look closely at the patina of the piece. Wood furniture tends to lose its natural color over time, especially if the piece sat outside. Look for any signs that the piece has multiple coats of paint or stain as well, as this indicates that the piece passed through multiple owners and has some age to it.
Check the piece over and find any signs of glue or screws. If the piece has dowels or pegs holding the pieces together, then it is likely an older piece or an antique. Only modern pieces are made with glue and screws indicate that the piece dates from the 20th century.
Open any drawers on the table and examine the construction on the corners. If the drawers have side channels that slip into runners, then the piece may be from the 18th century or earlier. Drawers with runners placed underneath are from the Queen Anne period or later.
Use a magnifying glass to examine any screws used in the construction. Early screws were forged by hand and have a rough or crude exterior. Older pieces will have mismatched screws that were clearly made by hand. Newer pieces have screws of a uniform appearance.