(I'll try to work towards a nicer formulation of this eventually.)
The cardinal rules:
- Create your own journal and update it regularly. It matters less how often you do it as much as whether you're regularly updating it (pick a schedule, any schedule, and stick to it!). Aside from that respond to people's comments on your journal when they comment. It's a bit like seeding a garden by season but watering your plants when they need it. Seriously, people will lock in on your schedule once you maintain one. Don't fail them.
- Comment on other people's journals. You definitely don't have to comment on all journals. It's better to seek out journals you find interesting and engage with them consistently on a regular basis than engaging everywhere at random in time or space. They in turn may come back to your own journal. This gets the ball rolling and this is how connections are built. Historically MMGs have formed from these informal mutual journal relationships. Exceptions exist, but they are not the norm. This is how connections are made.
- It increases the chances of people checking out your own journal (and commenting on it) if you focus on quality comments over "quantity comments". What is quality? It's simply a comment that one has put some thought/feeling into. For example, an "I agree" one-liner is nice, but it's not something that's likely to make anyone go looking for your journal. In particular, it's possible to make a "career" as a valued community member simply by being a good commenter.
- Read http://www.albion.com/netiquette/rule2.html and think about how you're posting and what you're posting. If you don't want to see something (like your exact NW, your political opinions, ... or even what you really think about your mother in law) end up on the front page of the news, forwarded to the inbox of friends and family or your boss, or recorded by various governments, you should never post it electronically. You might even consider never writing it down. Keep in mind that privacy is not an absolute. It's rather a matter of which degree an adversary will go towards finding it out if you triggered or pissed them off. There are two strategies here. Either live in a way that doesn't create adversaries xor refrain from saying anything that can be used against you. It is wise to think about this not just on the forum but also life in in general. Cleaning stuff up later is a pain and it will only go so far.