For the occasional remote support situation, I've used Fog Creek's Copilot: https://www.copilot.com/
I'm honestly not sure how it compares feature-wise with other solutions, but it has a few attributes that make it work well for me (I only need to do this kind of thing a couple times a year):
- it's drop-dead simple for the other person to get it going. When I need to use this, the other person I'm helping is generally a completely non-technical user. They just want their printer or whatever to work, and opening an email is about all that I can ask them to do (and have done correctly). And that's about all I have to ask them to do to get Copilot working. And if email is the problem, there's a relatively simple code that can be given over the phone.
- it's free on the weekend. Since I'm typically doing this for friends and family, the weekend is often when I need this anyway, and if not it's usually OK to wait until then. If the problem can't wait, it's only $5 for a day-pass, and either party can pay.
- it uses a server to mediate connecting through a firewall - essential for what I need to do.