Regular Spanish verbs are actually pretty easy to remember, but you wouldn't know that from looking at the -ar, -er, -ir conjugation charts from Wiktionary.

I made a chart that summarizes all three conjugations, highlighting where they are the same. It is as concise as humanly possible.

Spanish Verb Chart

Example words for each conjugation are hablar, comer, recibir.

The -er and -ir conjugations are often the same. When they are, I simply put a dash, indicating a repetition. For example, 2nd person present is a/e/- s, which is a/e/e s, which is as/es/es, which means hablas, comes, recibes.

I highlighted two patterns. First, the blue cells highlights the forms which are most predictable. For example, look at the 1st person plural conditional a/e/i ríamos. If you look to the right, the only thing that changes is the suffix indicating person—mos becomes is, but a/e/i ría stays the same. And that change is the same for all blue cells. Look at the 1st person plural imperfect subjunctive á/ié/- semos. Again as you look rightwards to the 2nd person plural, mos becomes is. And once more right, is becomes n.

Second, the red cells highlight forms which are like the present subjunctive. They exhibit what I think of as "vowel-inversion". The a becomes e and vice versa.

Finally, I should explain the indicative imperfect. What's up with that struck-through b?

It shows that there actually is no b in the form, even though a b is written later. So a/íb/- ba means ab/í/- a means hablaba, comía, recibía.

But the struck-through b is the better way to remember it for me. In Latin, all verb conjugations have a ba in the imperfect. bam, bas, bant, bamus, batis, bant still rings in my ears, even eight years after my last Latin class. It's just that, due to a sound change in Spanish, the b was dropped. You can still see it in the fact that there is an accent mark over the í. When the b was there, normal Spanish stress rules made the i stressed. But when the b was lost, the stress stayed, necessitating the accent mark.