Been working remotely since the turn of the century. The answers to all these depend on whether there is a place where most of the team is located, or whether it's a totally distributed team. Also depend on whether the new person is new to your team but not the company and/or new to working remotely from their team, and working from home versus working in a remote site. So adapt as needed.

For on-boarding, if there is a large mass of people in one site, then bringing the person in relatively early in on-boarding is really helpful. It builds connections that can make it easier to ask questions after the new hire has returned home, and allows for faster acclimation to startup, plus a way to peek over other people's shoulders to see how they use tools, interact, mannerisms, etc. Makes it easier to feel like a part of the team.

If there's not a site where there's a critical mass of employees, but there is one or more colleagues nearby, it can be worth it to set up a welcome lunch get together just so that the new employee has at least one IRL contact. If not, well, that's fine too.

As manager/team lead, spend lots of time with the new person on tools, culture, etc. Introduction, video chat, etc. from the start, plus your communication tools (hangouts, skype, GoToMeeting, whatever for collaboration). Everything you'd do for an employee on-site (if that's a thing), plus more frequent check-ins because you can't see face and body language as easily, and are not necessarily yet as familiar with communication patterns. Establish your minimum requirements for things like status/tasks/synchronization. You'll learn to interpret your new hire's patterns (is that silence because she's thinking or because she's distracted or because she disagrees) over time, but at first, ask and wait, especially if your new employee is new to remote work and doesn't yet know how to maintain communication from afar. But that's part of any on-boarding.

Make sure that the kit that the new hire gets includes a decent headset from the start - this is critical for participating fully.

For a distributed team, getting together can be crucial, but there have also been times when I haven't gotten together with teammates for a couple of years, and some I've never met IRL. Different continents, too costly, etc. If/when you do get everyone together, plan for real work as well as downtime and team building, and remember that folks who work remotely aren't necessarily used to being surrounded by their colleagues and always being "on" in the same way. Plan meals and expect some to opt out. Allow for jetlag if people are coming from far-away places. Have an agenda, and also have time for some sort of team-building activities, even if they're simple things like a picnic in the park or a play or beach outing or something.

Also, if you're doing a retreat type thing or renting house/resort together for out of town folks, please be cognizant of individual differences, and any outliers. The lone vegan or omnivore or person with hearing challenges or mobility issues doesn't have any issues working at their regular location, but at a group gathering, those challenges can loom large enough to be serious impediments to the goal of connecting coworkers. I'm often the only woman in the call or on the conference room, but there is no way I will be the only woman in the house so don't rent a single AirBnB and expect me to attend comfortably while sharing a bathroom with my male colleagues and eating breakfast in our jammies. OTOH, being the only one NOT in the house is just as bad as still being remote. Of course, other individuals not have an issue with these sorts of things. So think through these F2F meetings, especially for smaller companies. As with all remote worker issues, the key is to make it visible by talking with everyone involved about issues and concerns before the get-together.