Work in this order:
1. Read the initial sign: أ، ن، ت، ي.
2. Read the ending: singular, dual, or plural.
3. Decide third person, second person, or first person.
4. Check masculine or feminine where the paradigm distinguishes them.
5. Finally notice the middle-radical vowel to identify يَفْعَلُ، يَفْعِلُ، or يَفْعُلُ.
This method is safer than guessing from the first letter alone.