Aromatic (more stable than its open chain counter part)
If :
1) cyclic (is a ring)
2) flat ( kinda hard to know unless memorized which are and which aren't)
3) has 4n+ 2 number of electrions (Huckels rule)
simply if has these number of electrons 6,10,14,18 ect. add by 4's
4) has a P orbital at every carbon (is conjugated) ( if has double bond then has p orbital and if has free electrons with a minus sign then has a P orbital at that carbon or if a carbon cation)
Anti aromatic (less stable then its open chain counter part)
1) cyclic
2) has 4n number of electrons ( simply 0,4,8,12 etc. # of electrons)
3) not flat
4) has a P orbital at every carbon
Non- aromatic
1) not cyclic (not a ring)
2) has a carbon with no P orbital (example sp3 carbon)