Comforting the Depressed - Be Available
This is part of a series and I would recommend starting from the beginning if you have not done so already. You can find all the posts in the series under the tag "Comforting the Depressed".
Be there, but also be active. Reach out.
This is a huge variable that depends entirely on the nature of the relationship between the two people. But, if your intention is to comfort more than a one-off, being available for support is a massive help. As I said, the level of availability depends: it can be from "You can text me if you ever just need to make smalltalk", "You can text me if you're feeling down", to "You can call if you're feeling lonely or overwhelmed", to "You can call me literally day or night if you're in a crisis".
This being said, the important thing is to set boundaries, and to set them explicitly. Both parties need to know exactly the extent of the support that you're willing/able to give. Because if they reach out to you (a form of vulnerability) and you decline (which is your right and not necessarily selfish), that hurts. And it can make them feel like you aren't there for them at all when that isn't the case. This is a case where both parties have to understand that one cannot depend solely on one other person. This post is about the comfortee, but the mental health of the comforter is just as important. There shouldn't be a sacrifice of well-being out of obligation (or even with best of intentions) because the old adage of "on an airplane put your own mask on before helping others".
Beyond being available, reaching out can be such a big deal to those dealing with mental illness. Even if you're at the most basic level where you play a video game or watch a movie with them every once and a while, meet up for board games, or chat about a TV show over text: it doesn't always have to be deep stuff. It's about connection, and sometimes that's as simple as just talking, about anything. It shows that you care, it shows that they aren't forgotten or invisible.
It also helps them remove the burden of reaching out for help, which quite often can be very hard if they feel as though they are bothering you, start to doubt that you care, etc. Reaching out -whether it be messages, phone calls, Facebook messages, Facetime, or good old IRL hangouts, is huge.
Another point that people (including those with the depression) is being helpful; my depression often makes me feel like a child: I don't do laundry, clean my apartment, or make appointments regularly. Some days I can't even shower, brush my teeth, or get out of bed. But a few times on those days, I've hopped on a depression support chat room and said "Hey, can someone please help me get motivated to shower?" and all it took was a few people saying kind words, and that was enough. So beyond validation of what in their life is hard -trivial or not- helping out when you can for everyday things can make a huge difference in their life, not only for their quality of life (showers improve my mood 100-fold) but also it's another form of validation. And an act of care.
And -surprise surprise- be sincere. If you ask someone to hang out then, say, invite along a ton of friends and barely treat you like you even exist: guess what, that's not being available. That's just being close in proximity. That's not to say that it has to be one-on-one; personally being invited into a friend's group of friends helped me form more friendships, further strengthening my support system. But meeting new people takes much more energy for those in the midst of depression than it would seem at first glance. So you bloody well better actively try to include them and ensure they're comfortable in a new crowd.