MaverickGirl's 5 part guide:

https://www.coolstuffinc.com/a/kendrasmith-12112019-the-ultimate-pauper-elves-primer-an-introduction

https://www.coolstuffinc.com/a/kendrasmith-12182019-the-ultimate-pauper-elves-primer-the-other-cards

https://www.coolstuffinc.com/a/kendrasmith-12272019-the-ultimate-pauper-elves-primer-sideboard-cards

https://www.coolstuffinc.com/a/kendrasmith-01032020-the-ultimate-pauper-elves-primer-matchups

https://www.coolstuffinc.com/a/kendrasmith-01102020-the-ultimate-pauper-elves-primer-sideboarding

And some amazing tips (very detailed!):

https://www.reddit.com/r/Pauper/comments/icb063/10_pauper_elves_tips/

I wrote these tips for myself, but maybe other people will like them too. If you can think of any other tips for playing Elves, please share them in the comments!

Morphs (i.e. flipped Birchlore Rangers) are colorless. Among other things they can:

Block and deal damage to Guardian of the Guildpact.

Block and deal damage to Mono White Heroics creatures when they have protection from green.

Deal damage through Prismatic Strands.

You can tap your creatures during the Declare Attackers Step after Provoke triggers resolved. Thus, they won't be able to block what provoked them.

Birchlore Rangers help you tap creatures that have summoning sickness and creatures that don't have any tap ability.

You don't have to name "Elf" with Distant Melody. If naming Elf would deck you, you can name "Druid" or "Warrior" or "Scout" etc.

If you would like to go for a Timberwatch kill, but you only have one more creature than your opponent (counting your Timberwatches too), then you can attack with all of your creatures (Timberwatch Elves included), let your opponent declare blockers, then untap with Quirion Rangers as many Timberwatch Elves as you want and tap them to pump the unblocked creature, whichever it is.

If you put very important noncreature cards on the bottom of your library with Lead the Stampede, you can reshuffle your library with Sylvan Ranger in order to maximize your chances of drawing said noncreature cards. Thus, sometimes it can be useful to hold a Sylvan Ranger in hand.

Don't play out your Island if you can play a Forest instead and you don't need blue mana right away. Later in the game you will need as many forests in play as you can in order to have many Quirion Ranger activations available.

If you already have a Birchlore Ranger and your opponent isn't likely going to kill it, consider fetching a Forest with Sylvan Ranger. Later in the game you will need as many forests in play as you can in order to have many Quirion Ranger activations available.

Quirion Rangers also make it easier to leave up instants for your opponent's turn.

You can cast a conspired Gleeful Sabotage on turn 2 if you have a Forest, a mana dork and a Quirion Ranger between opening hand and first draws.

[For paper play] Priest of Titania, Timberwatch Elf, Elvish Vanguard and Wellwisher count your opponent's elves too (Gladecover Scout, Carapace Forger, Silhana Ledgewalker etc).

EDIT: Formatting.
RE-EDIT: I have three additional tips for who's still here :)
(the first two of these were suggested by _ZodiaK)

When you want to play around Echoing spells you can start casting Birchlore Rangers as Morphs. In fact Morphs don't have a name, so not only if the opponent targets a Birchlore Ranger, Morphs will be safe, but if they target one of the Morphs, the other Morphs will be safe as well.

Quirion Ranger can target any creature in play. Thus, you can kill illusions with Quirion Ranger activations.

If your opponent has a Flagbearer in play, you have to target it with Quirion Ranger. Sure, this is quite obnoxious, but it still doesn't stop you from making additional land drops by activating Quirion Ranger on the Flagbearer.