
Classes with Class
In 2004 and 2005 Skip Williams (co-creator of Dungeons & Dragons 3rd Edition) put a series of articles on the Wizards website with tips on playing each of the various character types. Wizards of the Coast has moved them to their D&D Archives, but you can still find them there if you are diligent in your search.
These are an excellent reference. They were written for D&D 3.5 but even if you are running a fifth edition game you will find then a useful reference.
Here are direct links to them:
Fighters with Class
Rogues with Class
Wizards with Class
Clerics with Class
Barbarians with Class
Bards with Class
Sorcerers with Class
Druids with Class
Rangers with Class
Paladins with Class
Monks with Class
Warlocks with Class
And here is a link to the 3.5 D&D Archives page:
3.5 D&D Archives