Spanish Verb Analysis
The stats below are derived from a dictionary of around 1,800 Spanish verbs. As it's not a complete list of every verb ever used, the stats are not perfectly accurate. On the other hand, they may more closely represent "every-day Spanish."
Verb Endings
All Spanish verbs end in -ar, -er, or -ir. However, they are not divided equally:

Next time you forget how a verb ends, might as well guess -ar.
Verbs with Identical Stems
Because of the way Spanish verbs are conjugated, if two verbs share identical stems (the bit that remains after removing -ar, -er, or -ir), some of their conjugated forms might be identical.
Does this ever happen in Spanish? Yes, but luckily there are only four verb pairs that share a stem:
asar v. to pester, to roast
asir v. to grasp, to seize, to take root
These would share the regular first person present tense conjugation (aso), but asir is irregular in this tense (asgo).
asentar v. to set up, to place, to seat, to flatten, to sharpen, to set down
asentir v. to agree, to assent
These share the regular first person present tense conjugation: asiento
sentar v. to seat, to establish, to place, to sit
sentir v. to regret, to feel, to sense, to feel sorry
These share the regular first person present tense conjugation: siento
crear v. to create, to set up
creer v. to believe, to think
These share the regular first person present tense conjugation: creo
Notice that every pair includes one -ar verb. If an -er and an -ir verb were to share a stem, they would have identical normal conjugations in around 17 cases.
Luckily that never happens in Spanish.
Verb Prefixes
As in English, sometimes you can add a prefix (like, well, 'pre') to a verb and create another verb. When that happens, the two verbs often have similar (and sometimes identical) meanings. For example, decir means "to tell" and predecir means "to foretell."
Common verb prefixes in Spanish: a-, con-, de-, en-, in-, pre-, re-