Sending a customised welcome message is the first touchpoint for the user within the community. You want to be sure you're doing a good job at being able to guide the user towards next step, while making the user feel at home with the community.
A detailed onboarding form helps you capture user's goals and interests thoroughly. This helps you customise your approach to help user gain more value from the community.
Having a well thought of onboarding journey, with you being able to deliver value instantly is what is going to make the users stick around for more.
Every new member introduction is a user's first entry point in the community - make sure you acknowledge and respond soon enough on each post.
A buddy system in the community helps new users navigate easily through the community. As step one, get opt-ins from members with certain level of experience who would want to volunteer for the buddy system. Next, match interests and pair new members with their respective buddy.
Well, it is fairly easy to get overwhelmed will all the content you got running for the community - isn't it? But don't let the user get overwhelmed in the first few days - here's a thought process on how you can carefully pick the content you want your user to access for the first few days.