The Advice Everyone Repeats Is Half Wrong
The standard advice is to open with vowels. Counted across all 12,578 five letter words in the list this site uses, the letters that actually turn up most often are S 46 percent, E 44 percent, A 41 percent, R 30 percent, O 30 percent. S beats every vowel except E, and it beats E. An opener packed with vowels and no S or R is leaving information on the table.
Position Matters As Much As Frequency
A letter being common is not the same as it being common where you put it. The most frequent letter in each of the five positions, first to last, runs SCB then AOE then ARI then EAT then SEY. S is the most common first letter and the most common last letter, for two completely different reasons: plurals at the end, and S-blends like ST and SC at the start.
What To Do With That
Pick an opener that covers high-frequency letters in the positions they actually occupy, then a second guess that covers a different set entirely rather than re-testing letters you already know about. Once you have two rows of clues, the Wordle Solver will show you every word still standing and rank them by how much each one would tell you.
One Caveat Worth Knowing
These counts are over every five letter word in a tournament dictionary. The puzzle draws its answers from a much smaller curated list of words ordinary people know, which skews slightly away from obscure entries. The direction of the advice does not change, but do not expect the percentages to predict answers exactly.
More like this in the guides index, or put your own letters into the Word Unscrambler.