Choose by flavour first
If you like cappuccino, look for chocolate, nuts, caramel or dried fruit. If you drink straight espresso, you may enjoy more acidity and fruit.
Do not buy coffee just because it sounds rare. Buy for the drinks you make most.
Fresh, but not too fresh
Freshly roasted coffee is good, but espresso often behaves better after a short rest. Very fresh beans can be lively and hard to dial in.
Once opened, store beans airtight and away from heat and light.
Roast level
A very light roast can be delicious but often asks more from grinder, water and technique. A medium or medium-dark roast is usually friendlier at home.
For first setups, choose forgiving beans before chasing extreme flavour profiles.
Keep notes
Write down which beans worked well with your machine and grinder. After a few bags you will know your own espresso profile.
That small habit saves money and makes future buying easier.