This is very much a rule of thumb but it works in almost all cases. All you need do is memorize verbs as pairs and you should almost always be able to tell which is the perfectiv as long as you remember the order in this table.
The biggest exceptions are the verbs without pairs. Some of these pairless verbs are perfectiv, some imperfectiv and some hav duel aspect. Another complication is that some imperfectiv verbs hav two perfectiv "pairs" and each of these perfectiv verbs take a different shade of meaning of the imperfectiv verb. One or two verbs differ only by stress - I think there is a pattern here as well but, as I'v only encountered two so far, I'm not sticking my neck out.
I'm no expert on Serbo-Croat. There may be weaknesses in this method that I havn't yet encountered but it works for me. Try it and see if it works for you.
Confusing aspects is the surest sign of someone who is not a native speaker. Get this right and you're sure to impress.
Finally, if you want to get the hang of aspect, you need a dictionary which givs the verbs as perfectiv-imperfectiv pairs. The only one that does this is the SerboCroatian-English Dictionary of Morton Benson. Benson takes cross referencing to ridiculous extremes but a side effect of this is that if you look up any verb you will always find it listed with its pair if a pair exists.
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Spelling convention: Superfluous 'e's are dropped after 'v'.