The number one thing is always to dive with a buddy that's for safety first. You never want to dive alone, you never know what the conditions could change, and you never know what could happen.  So always dive with a buddy.

Tip number two find yourself a mask that fits you properly.  

It's essential that you find the right scuba gear that fits you right. So that you're comfortable in the water if you constantly have to readjust your mask.  And there's water leaking into it you're going to feel more anxious and you're going to have to readjust your mask.  And it's going to overall dampen the experience of your first free dive.

So if you can go to a certified diet shop and have them go over the proper mask with you have them fit it properly. It's going to make your first dive a much more fun experience.

A good way to tell if your mask fits properly is to put the mask on your face first without the strap over the back of your head and you suck in through your nose. It'll suction cup to your face if no air is leaking anywhere around your face then you know it fits right. If you feel air leaking in or if it pops off right away, you know that your mask is too big and doesn't fit right. Second,  along with the gear make sure you have a snorkel that fits in your mouth and you're comfortable with. 

The number one thing, when you're diving is as soon as you do your duck dive make sure you take that snorkel out. Because when you're coming up, you have the snorkel in your mouth. You will not be able to breathe properly when you get to the surface. You're not going to be able to do your breath in before you're in-breath,  so make sure you take the snorkel out when you're diving. You need to prevent your mask from fogging. 

Another good tip I would have is to practice doing your breaths-ups outside of the water first. So when you know that you have a free dive coming up a few days in advance,  maybe a few weeks in advance practice doing your breathe-ups statically or on land. 

This will allow you to get used to breathing in, breathing out, completely breathing back in, and then holding your breath. 

Having pressure inside your lungs get used to feeling uncomfortable with how much pressure is in there and then try to hold it for as long as you can you might feel lightheaded.