I really like Web DM's discussion about this and recommend watching/listening to it:
https://www.youtube.com/watch?v=S-nO8vIJP-E
In my last campaign, a character multi-classed into a warlock. The patron was an arch fey. She expected that certain tasks and quests be completed for her. Often these had little effect on the party. In other instances, they would be the impetus for the parties quest. Most of her interaction with the character were via a Satyr who would relay messages, instructions, and deliver and retrieve items.
One thing that I did, which I thought worked well, as I had her reward the character with a magic artifact (based off of an ENWorld En5ider article on Fey world magic items, whose title is escaping me at the moment). The more powerful effects of this item required accepting a geas from the Arch Fey. The mid-range power required doing something to impress the Fey patron. If you succeed, then she gives you the boon, if not, you might be punished for bothering her with trivial feats not worth her attention much less a boon. That magic item did more to make the patronage feel an important part of the game than the class mechanics did and I think in the future, I would also have the character receive magic items from the patron with similar mechanics.
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UPDATE:
The article was EN5ider 92 - Armament of the Courts, by Colin McLaughlin. I tweaked the "Horn of Winter" to fit my campaign and the character.
But the mechanics that I like from the items in this article are:
Legendary Deed: basically you offer a tale of your deed to your archfey patron. If accepted, the magic items gain some temporary powers. If not, the character suffers some penalty.
Royal Will: Once every month and a day, during a long rest, you can become receptive to the will of your arch-fey patron and you have a geas placed upon you (automatic failure of any save). Once you complete the objective of the geas, the item receives an especially powerful, but temporary, property or power.
I liked this so much that I would seriously consider making this a homebrew addition to the warlock class. Either an item or powers that can only be unlocked by offering up legendary deeds or taking on compulsory quests.