Accents on letters a, i and u do not change the pronunciation of the vowel. Accents on letters e and o do. é is closer than è and ê. The first one is between English i in bit and e in bed. The last two ones are just the same as English e in bed. ô is always closed in standard French of Nothern France, this rule does not apply in the South. Saying this, here are the tricks: à is used in few words: à (at, to), çà (çà et là: here and there), deçà (en deçà: below, beneath a certain amount), déjà (already), là (here, there) (can't think of other examples right now) The circumflex accent ^ is usually used to indicate that there used to be another letter here, most commonly and old 's' that disappeared. Just think of FR 'hôtel' and EN 'hostel', FR 'château' and EN 'castle'. However in few words, the circumflex indicate a grammatical hommophone: dû that is the past participle of verbe devoir to differentiate it from du = de le, crû that is the past participle of verbe croître, to differentiate it from cru the past participle of verbe croire (these two verbes share many orally identical forms that are written different by the addition of a circumflex accent for croître. You may also consider that croître comes from croissance, hence the ^ when the sound s is missing), mûr (ripe) from mur (wall)… Last one ù is used in one word to differentiate homophones: où (where) from ou (or).

The accents have specific pronunciation. (à) - ah- is used in french and means (to), not (á) (â) & (ô) is used in the tense "passe simple," which is for proper story telling (è) is -uh- and is important and is usually for pronunciation purposes (é) is -ay- and is important because is turns verbs into adjectives and is mostly pronunciation purposes