There are not too many irregular verbs in Latin, but this is one of them. You can see a complete conjugation here (click on the little "show" arrow to see the conjugation displayed). This is one of those Latin words where the spelling alternates between "o" and "u" - so you can find the forms volt and vult, for example, although the spelling with "u" is more common.
This verb also provides the basis for some compound verbs: nolo = (non volo) and malo (= magis volo). These compound verbs reflect the irregularities of volo, so it is worth becoming familiar with their conjugations. Click on the links if you want to take a look at the conjugation charts for these verbs. Another important contracted form is sis, meaning "please" = si vis, if you will. So, be careful when you run into the word sis: it could be the 2nd person subjunctive of "to be" but it might also just mean "please," si vis.
One of the hardest things about this word in Latin is that there is not a simple one-to-one equivalence with an English word. Sometimes when you say in English "I want" it means volo in Latin... but it can also mean peto or cupio or opto or even desidero, depending on just what kind of "wanting" is involved. In addition, volo often means something more like "I am willing" (rather than "wanting"), meaning something that is a matter of intention and purpose, rather than wishing or wanting. So, the best way to get a sense of how this Latin word works and its wide range of meaning is just to read and read and read lots of Latin, paying special attention each time you find an instance of the verb volo and thinking about what the word seems to mean in that specific context.
In terms of usage, the Latin word can take an infinitive: potare ego hodie tecum volo, for example, as you can read in Plautus. It can also take an accusative plus an infinitive: hoc volo scire te, "I want you to know this" (since we do something similar in English, it's pretty easy to understand this Latin construction. Much more rarely you can find volo used with ut or ne to express purpose, but the infinitive constructions are far more common.
Note that the phrase volo dicere means "I mean," in the sense of "I mean to say." This can also be used to ask a question about what something means: quid vult? "what does (it) mean?"
Here are some examples of today's word in Latin sayings and proverbs; for more information, see the page at the Scala Sapientiae, which contains notes on some of the proverbs cited below, as well as additional proverbs:Deo Volente
Deus dat cui vult.
Si vis, potes.
Aliud est velle, aliud posse.
Quod vis videri, esto.
Si non ut volumus, tamen ut possumus.
Sic dii voluerunt.
Cum dixeris quod vis, audies quod non vis.
Si vis amari, ama.
Da, si vis accipere.
Nos iubere volumus, non iuberi.
Id quod volunt, credunt quoque.
Vivimus, non ut volumus, sed ut possumus.
Quod tibi vis fieri, hoc fac alteri.
Quod tibi non vis, alteri ne facias.
Si vis scire, doce.
Volo, non valeo.
Fac bene dum vivis, post mortem vivere si vis.
Bene vivere omnes volumus, at non possumus.
Bene vixit is, qui potuit, cum voluit, mori.