What are Exchange Letters?
If you are looking into Fandom Exchanges, chances are you have seen "Letters" mentioned.
Sometimes called a Dear Creator letter, exchange letters are optional, but incredibly helpful, documents to have on hand when signing up for a fanwork exchange. Letters include more in-depth information about the type of gift you would like to receive than typically goes in the AO3 "Prompt" box. Broadly speaking, letters should contain everything your gift-giver would need to know in order to create art or fic you would enjoy. This may include, but is not limited to: general likes and preferences, Do Not Wants (DNWs), ship- or character-specific interests, and OC information. Whether you're writing your first letter or revising your current one, read on to learn more about exchange letters!
Some information in this post has been adapted from the guide created by @enigmalea for @arlathanxchange. Check out their other tutorials for AO3 here!
Do you need a letter?
Not unless the event specifically requires them. Plenty of fans participate in exchanges without a Letter. If you decide not to put together a Letter, it's still a good idea to keep in mind the fact that someone will want to make a gift that you enjoy during this exchange - so leaving good prompts, likes, and DNWs in your official requests is still important!
What should an exchange letter include?
General likes and preferences
If someone is creating a gift for you, they'll need to know what you like! This can include relationship types (romantic, platonic, poly, etc.), tropes (angst, enemies to lovers, only one bed, found family, etc.), AUs, kinks, and art preferences, among other things. If you're not sure where to start, scroll through your AO3 bookmarks/history and think about the Additional Tags you see repeated often, or the ones you use to filter when deciding what to read.
Fandom-specific likes and preferences & ship- or character-specific interests
If the exchange is for a specific fandom/ship/character, you may wish to include specific elements that draw you to that theme! For Dragon Age, this may include things like mage/templar dynamics, Antivan Crows, Elvhenan AUs, Qunari cultures and customs... the possibilities are endless. If you're not sure where to start, check your AO3 tags as described above. You may also consider the types of PCs you like to play, your favorite NPCs, and what draws you to those storylines.
Do Not Wants (DNWs)
In most exchanges, unlike general likes & preferences, Do Not Wants are a hard line for creators. This means that anything you list as a DNW must be avoided by the creator. Think about any squicks you avoid, triggers you might have, tags or ships you exclude when searching, or things that just make you hit the back button and not read a fic. More specifically, you can include things like specific points of view, tenses, styles of writing, general tropes (fluff, angst, smut, etc.), or more specific tropes (whump, D/S dynamics, modern AU, etc.). As with likes and preferences, you can also list fandom, ship, or character-specific DNWs (MCIT, Fen'harel vallaslin, mage/templar relationships, etc.). It is best to avoid being overly broad with your DNWs. Listing things such as "bad people", "hardcore BDSM", and "non-vanilla sex" are confusing for creators to follow and difficult for moderators to enforce. What does bad mean to you? Hardcore? Vanilla? Everyone draws the line on these things in different places - it is best not to assume, even if you think the line is "obvious". It is also best to avoid DNWs that add an unfair burden on your creator. This may include DNWs that force them to create for a specific prompt (DNW: art other than the pose/setting listed), force them to create a crossover work in a single-fandom exchange, or make your gift impossible to create (DNW: Anders mentioned by name in my Handers request). That being said, most exchanges understand that it is near impossible to create an exhaustive DNW list, especially if you're new to exchanges. Most events accept a broad "DNW: kinks other than requested", which allows you to request specific things you know you enjoy, but avoid landmines of squicks you might not even be aware of.
Information about your original characters
If the exchange you're participating in allows original characters, you may wish to include information about your OCs, as a reference for your creator. Since the AO3 prompt box is limited in both space and formatting options, your letter can be a good place to include more detailed backstory & personality information, what they're like in the relationship(s) requested, and reference images or links to reference images of your OC's appearance.
Where can I host my exchange letter?
Google Docs
Google docs is a popular option for hosting letters, particularly if you want to include a lot of text or images, but are not familiar with code. You can easily create a table of contents, link to other docs and external sites, add images, make lists and tables, and generally format your letter in an easy-to-follow manner. If you use Google docs, make sure to update the Sharing settings so that anyone with the link can view the document (not comment or edit), otherwise your creator won't be able to see any of your information!
Tumblr
You can also create your letter as a regular tumblr post or page. This is good option for limited or shorter letters - if you are going in depth, or your lists of likes and DNWs are longer, the length of your post may get unwieldy. Be careful if you use a page (yoururl.tumblr.com/pagename), rather than a post (created via the "Create" button). Mobile users are frequently redirected to blog homepages when attempting to access a page, and may not be able to view a letter hosted there.
Dreamwidth/Wordpress/Other Blogging Site
Although not as widely used or as popular for fandom uses as tumblr, Dreamwidth, Wordpress, and other blogging sites are viable options for letter hosting! If you already have a presence on those sites, or if you prefer to avoid the other hosting options for whatever reason, these may be the choice for you.
Free Webhosts - No/Low Coding Required
Google Sites - free as long as you have a gmail account. Includes basic templates that make it quick and simple to build a site for your letter info. Wix or Weebly - has a site builder with templates, but allows you to do some coding if you'd like. Free, but will force a banner on your site unless you upgrade to a paid plan.
Free Webhosts - Coding Required
Neocities - an homage to the old school geocities. They offer a large amount of space and allow all content, including adult content. Netlify and Vercel - free webhosting with other benefits like automatic deployment from Github. More complicated than is necessary for an exchange letter alone, especially if you're just starting out, but these are a great resource for anyone with coding knowledge who wants to build a website.
Note: Per AO3 terms of service, exchange letters are NOT allowed to be posted as separate works on AO3. Although, you are permitted to list general likes/preferences in your profile, space and formatting options are relatively limited, and generally surpassed by one of the other options above.