Get you self a copy of the periodic table that shows pictures of the elements. This one is good:
You will see that the majority of the elements are solids, so the easiest thing to do is to look at those that are not solids.
There are a few gases, H, He, N, O, F, Ne, Cl, Ar Kr, Xe. These are either low atomic number elements (H, He) or in the top right of the periodic table (N, O, F, Cl) or are noble gases (Ar, Kr, Xe), again far right of the periodic table.
There are only two elements that are liquids at STP, Hg and Br.
I remember that these few are liquids or gases, then the rest are solids.