Yo!
Generally, stuff that are diatomic, ex. chlorine and hydrogen gas, are covalent. Anything that will share electrons are covalent (draw the Lewis diagrams, it helps)
Ionic stuff are generally stuff from Group 1 and Group 7 (far left and far right) of the elements in the periodic table. Generally, ionic compounds are solids. Ex. NaCl, KCl, CaO. Hopefully that helps!