February is the month chosen for some letter writing projects, because it is the shortest month of the year.
A Month of Letters (LetterMo) was started by someone who took a month off from the internet and wanted friends/colleagues/people to communicate with her via the written word. She enjoyed it so she thought she would promote correspondence via letter/snail mail in 2012. I found out about it via another postal project, Postcrossing, and took part that year. The idea is to send an item of post every postal day, be it handwritten, typed, postcard, mailart... and also encouraged you to post in different postboxes, and variety of what you mailed.
International Correspondence Writing Month (InCoWriMo) was started in 2013. I participated first time in 2014. The idea is to send a handwritten letter/card/postcard every day in February.
Through both projects, you can find strangers to write to. LetterMo asks that you pledge to reply to the letters you received, although not every letter I wrote through this project yielded a response. It might be difficult to reply to some letters but I feel their receipt should at least be acknowledged. LetterMo has a forum, and InCoWriMo allows for comments.
You may have also noticed there are two InCoWriMo sites, but they are not the same site or run by the same people. InCoWriMo-2019 is the continuation of an alternate site set up by a snail mail enthusiast when for unknown reasons, the original site was not updated one year.
On the alternate site, you can submit your address via a form, and you can have this displayed on their address page until early March, or continue to have it visible for most of the year. You can also leave comments on the pages (runs on Wordpress) but they are to be approved/moderated.
On the original site, you can comment using the Disqus system, and include your address to solicit for letters. Disqus comments aren't the easiest to navigate through. After a while, you lose the ability to edit your comments, but you can still delete them.
On LetterMo, you have a profile. You used to be able to put your address on, and this would be visible to the logged in members. Now, I believe it is restricted to friends - those you've sent/approved friendship requests. There is a forum you can leave your address in too and this section is not visible to those not logged in.
The February projects should promote the joy of letter writing. While 28 letters does not seem a lot to the seasoned letter writer, it can look a daunting task if you have other responsibilities taking up a lot of your time. Does it matter if you do not write a letter/card every (postal) day? No. Some things in life should take priority. Writing letters to (would-be) friends should be a pleasurable experience.
There are other letter writing projects throughout the year, April sees write_on and National Letter and Card Writing Month, then there is the week with the 9th October (World Post Day) to make up International Letter Writing Week. There are days for stationery, fountain pens, handwriting, ...
What do you write in a letter to a stranger? I can't answer this for everyone. One size does not fit all. All I can give is suggestions - little stories, the weather, your day, a little about yourself and your hobbies, something funny, something about the city/region you live in... I mentioned Postcrossing earlier - this is a project where you send and receive postcards, and the postcards you send should be of a quality you want to receive. This can also be applied to letters - send the sort of letters you would be happy to receive yourself. The letter needs to be legible. Especially if writing to someone abroad, please write the date with the name of the month (and not the number). 1/2/2019 to me means 1st of February, not the 2nd of January.
What to expect in February? Hand cramps? Paper cuts? Inky fingers? I have only experienced inky fingers doing the writing projects. It may take time to receive your first letter. Snail Mail it is. Some postal services are faster than others. Patience, I am told, is a virtue. If you do receive a letter, please thank the sender, either by writing them a letter/card, or, if you can't write a reply then you could comment either on the project's forum or page. Some people like to share incoming and outgoing mail on social media. If you choose to do this, please cover / blur the other person's address.