Linkedin is a professional social networking site. It's used to show off your skills and for recruiters to be able to find you easily. You can land contracts and meet other professionals in your industry. You can also, reach out to people in your field for joint businesses ventures or ask them to do things such as being a guest for your podcast. To get the most out of Linkedin, I recommend having professional photos made of yourself along with getting an amazing profile summary written about yourself. Also, reach out to other people in your field and try to connect. If you want to go crazy, you can also join groups that you do endorsement trading. You can list things that you are good at on your Linkedin page, and once you join these endorsement trading groups they will endorse you. I also recommend getting some reviews up on your profile!
I have used Skype many times. I've been in certain locations in the world that were just too expensive to call the landline, and sometimes we wouldn't have internet. I would get a "Skype-In" number which was basically just a local number that my family could call me on that would be routed my mobile phone. If you have access to the internet then you can just log in to Skype and do video chatting or have a normal call for free. A disadvantage to using VOIP would be that if your internet connection is slow, you'll get bad reception and won't be able to hear what you are saying to each other.
I use instant messaging daily. Depending on who I'm speaking to and what we are speaking about, will decide on which IM platform I'm speaking on. The first platform that I think everyone uses is Facebook Messenger. I ONLY use this messenger if I'm reaching out to someone for the first time to get a better way of speaking. I don't like it and it's not secure. As soon as I usually get in contact with them, I get them to download one of two programs. The best two IM software for me are Wickr Me and Signal Private Messenger. Both can be downloaded on PC or mobile and both are encrypted.
