Firstly welcome along.
The search button, top right of the forum is your best friend right now.
Type in how to find places, it's been covered very well many times before.
Then type your area in and read through the reports of places and decide which few you would like to visit.
Be courteous to any one you meet and respectful of any property you explore.
Unless you're one of the special self proclaimed 'saviours' of all things shiney decent explorers do not steal items or damage property, certainly don't graffiti, smash shit up or break doors down.
If you can walk into a place great but a bit of climbing isn't out of the ordinary either.
Do not take tools to force doors open or its classed as going equipped and you'll rightly be arrested if the snitches are called.
Do some research on your intended explore, find out what it was and when and what, if any, plans are for the future. Look into any areas or items you want to see specifically and where they are, visit those parts first.
Take note of any findings for your future report.
Take lots of pictures, frame them well, keep them well lit and in focus and straight, the more pictures you take the better choice you have when it comes to selecting a few to do a report later on. Find interesting angles or more importantly interesting subject matter, that could be a state of decay or an unusual object.
50 pictures of one handed out of focus, funny angle, dark shots of the same 4 walls as you run through playing chase with your mates is not what makes a good report.
Google maps is your best friend and local papers your second.
Always carry a small first aid kit.