Ah, the dreaded indie game DIY marketing phase. It's mad how some devs send one press release, do a pinch of Twitter over there, spend some money to advertise the trailer... And yet results aren't there.
You spend all this time supposedly doing the right thing, and nothing is coming out of it.
But would you ever develop your game without a plan? No GDD, no direction for the story, atmosphere or gameplay? The likely result wouldn't be so pretty, and you know it. And marketing is no different: it's not like whip-up magical stuff. And for that very reason, you actually can promote your game yourself if you're smart about it.
Define your game's strengths
The special qualities of your game should be driving your strategy. Everything you do in your communications will highlight those.
- Do you have a beautiful art style?
- How about music?
- Do some particular game mechanics stand out?
- Does your studio have a unique story?
- Is the plot impactful?
- What will players feel when playing?
... And your goals
Whether it's sales (numbers or money), growing a large and engaged community, making a mark on the scene for future games, or anything else, make sure you pin this down first thing. It's easier to reach your goals if you know what they are.
Create a timeline
Go back from your game's release date, and divide the year leading up to it (or however long you have) into phases: assets preparation and polish behind the scenes, announcement, previews, and release. If you're short on time, you might have to skip on some of those - but never ever the assets prep phase, you obviously want to give yourself the best chance (I'd assume.)
Once you've agreed the timeline with your team, add it all to your production calendar and remember it - set up reminders on every device you own if you have to.
In a lot of cases, this marketing timeline will have to change: production and third-party delays are common place.
Choose your activities carefully
Every action you take in marketing has a cost: time or money - sometimes both, y'know? Make the most of that spend.
Budget and time allowing though, the sky is the limit - almost. Plan what you do around what you're best at (or hire someone to do the rest, heh.)
TL;DR: It's harder to sail without a destination, duh.