Do what Bethesda did: keep quiet until the very last few months before release, then drop a bombshell and win E3.
This actually seems like a good idea.
After Fallout 3 I hoped Bethesda will sell/lend license to someone else, so they never make another Fallout game again. However in a week they released 2 great trailers, a gameplay, and they showed a lot of new features the game will have, and now I'm hyped.
I found it to be a better strategy then teasing for 2 years with a few materials. It shows confidence in their own product - and I like it.
It also assures people, that the game is ready, so it minimalizes chances for downgrade, false advertising, stripping features, etc.
CEO of CD Projekt Red seems to think similarly, and was also impressed and inspired by Bethesda's strategy.
“We’re impressed with Fallout 4’s rollout. They came on stage and said ‘It’s here, it’s real, and it’s coming out on this date.’ We’re going to do something similar. We’re going to wait [to reveal the game - Cyberpunk 2077] until we can show off a very meaningful piece of it.”