We arrived in Tulum after being ridiculously ripped off on the journey from Cancún... Word of advice go from the centre and not the airport, and get the local buses instead of the airport ADO bus. You should be paying only around 300 pesos which works out at about £13.
We stayed at Amorcito Corazón hostel which was delightfully clean and pretty sociable. It had a rooftop pool and also a banging free breakfast every morning. And air conditioning!!!!! (Which we were extremely thankful of after the few sweaty nights on Isla Holbox.)
We loved Tulum, however one thing to note is how far apart everything is. The beach is about 6km from the centre and would take forever to get to on foot, therefore bikes or taxis were the best way to get around. The beaches are absolutely incredible, like something from the front of a postcard. However we were surprised to see its all occupied by huge swanky hotels which you can then walk through to get to the beach. Had we been super rich we would've loved to do a night in one, though some you can pay to enter just for the day (Azulik). We heard from some other travellers you can rent Airbnb's by the beach which also could be a good idea if you wanted to be close by.
One thing you must do in Tulum is visit some of the famous Cenotes! They are basically like natural pools with the most crystal clear waters which you can swim in, surrounded by incredible fish and even turtles. It's pretty awesome. These secret underground caverns are formed when limestone caves in, leaving a hole in the earth that leads to a pool of often gorgeous turquoise-colored water. We went to Cenotes Cristal y Escondido which were cool, but the biggest one is Gran Cenote and we've genuinely never seen anything like it. Get up and go at 8am when it opens, it's at its best then. The water is so clear and you'll most likely have it to yourself. You even have to shower your body to remove any sun screen or mosquito spray that may affect the purity of the cenote.
The Tulum ruins are also really beautiful. They are extremely well preserved and what's really cool is they are right next to the beach.
Food wise - again the street food in Mexico really is your best bet, you can get tacos on the Main Street for literally 8 pesos which is equal to 40p... And they taste heavenly. We also found a fab little burrito bar called Burrito Amor. V cheap and incredible food.
We asked around for where to sit at the beach, because it is so huge and there's so many options. We were recommended a bar called La Eufemia - if you're ever in Tulum make sure to spend a day there. You don't pay for the beds (you do at most other beach bars) and can get a huge 1.2L beer for 70 pesos. They also have fab tacos, happy hour on cocktails etc and great music too.
If you are going out drinking, always look out for happy hours - most bars have them and they're all at different times. So you can hop from one to the other to save some cash. We stumbled upon a Cenote party in Cenote Clandestino one evening which was like nothing we've ever witnessed - the crystal clear water from the cenote was fully lit up with different coloured lights and you could swing from the rope swing into the water, whilst a DJ played techno music in the background. We didn't go to any of the clubs but there are loads all around the city centre, not so much around the beach.
Would recommend staying in Tulum for 3 or 4 nights, and potentially looking into hiring bikes, a scooter or even a car if you're there long enough.