Facts about Sri Lanka and things I would recommend
Two months, December 2017 and January 2018, are a lot of time to discover things and make mistakes...
If you are going to stay more than 30 days you will need an extended visa. Either you get it before going there in an embassy (instead of the online one for 30 days), or you have to extend it once there. For that, your passport needs to go to the Department of Immigration and Emigration, but you don't have to. So if you don't want to deal with the waiting there, you can always find people that will do it for you.
To drive, you need at least an International diving license. Officially, you need a paper that you get in Colombo. We didn't have any, and noone asks you the moment you rent a motorbike. We just got stopped once by the police, but we were really lucky and didn't get a fine. If you do drive, do it carefully and get out of the way of bigger things than you (mainly buses and trucks).
Right in the airport you can get the tourist sim card. It's valid for 30 days, so we got one outside. Data plans are really cheap and you can recharge them buying a card in almost every shop, specially useful in those places without reliable wifi (for example, cheap places next to the beach). We used Dialog and couldn't be happier.
There are plenty of ATMs. Some of them won't work with a foreign credit card (looking at you, BOC). Do not despair, I had to try 4 different ones once, but you will get money. HNB was my favourite, never had a problem. And do not get just multiples of 5000, XX900 will ensure at least some small bills. Changing big bills is sometimes tricky.
Like everywhere, be careful with your things. We sat in the back of packed buses with our things in front. We were sitting in a train door with our things two wagons away. And the time that we left the backpacks in the train just on top of us, someone managed to steal one. Keep an eye in your stuff, better save than sorry!
Sri lanka has big waves. If you surf, or want to learn to surf, it is the place to go. Snorkelling is nice too, but usually the visibility is not that great.
If you love turtles, you are lucky. Turtles are everywhere! My favourite places to see them swimming and chilling were Polehna and Mihiripenna Beach. Around Bentota we went to a Sea Turtle Conservation Center, and although I would not recommend it, for the price you can check it if your really want to. There are some Turtle points to see them laying eggs, but you can also ask locals around, some are happy walking with you in the night along the beach to try and find them (we were not lucky).
If you go to Haputale, take a bunch of pens with you. Kids around will spot you from far away and run to you to ask for a pen. We just had one with us, and the disappointment in their faces will haunt me.
We didn't visit a tea plantation for them to explain us the processing, but drove and walked through several ones.They are beautiful. Do it.
Adam's peak is not as challenging as we thought. We are not that fit and were up in about an two hours and a half, with a couple stops in between. If you are going in the night to see the sunrise, waiting up feels really windy and cold. Plan so you don't arrive too early, bring a dry shirt, and layers. The next couple of days your legs will be sore.
Yala or Udawala? Well, we wanted to go to Yala, but we tried it on Christmas day, and due to the limit of jeeps per day, we couldn't go inside. As backup plan, we went to Bundala, which is beautiful too, specially if you like birds. A couple days later, and due to our lack or elephants, we went to Udawalawa. We had to wait 2 hours to go inside, but then we got totally elephanted-out. So things to keep in mind: If you're going on Christmas week, or any other really busy day, you better get there soon. In Bundala we got a guide appart from our driver, and even if it is not necessary, since the drivers know where to go, made the experience more enjoyable!
Is the Lion rock worth it or is Pidurungala basically the same? I did both. We arrived to Sigiriya in the afternoon and went to Pidurungala to see the sunset, which was really nice. Next day, I got up soon and rushed to the Lion rock (alone, since Alex didn't want to pay the entrance fee). For me it was totally worth it, but I am really happy I bought the tickets and went straight up, and enjoyed the gardens and museum later. It does get really crowded. The views from up both places are basically the same, but personally, I find the gardens and the massive lion paws worth a visit. I was happy going to both.
Anuradhapura or Polonnawura? We just did the first one, and didn't find it particularly charming. We visited the free spots with a bike, maybe the "VIP" ruins are just stunning, but from far away we were not inclined to do them.
Eating and drinking
Food is spicy. Wonderful, but really spicy. Curry is always a great deal, as well as kottu and rottis. Sea food is fantastic.
Apparently alcohol licenses are very expensive. Most places don't have one. Some of them will still sell it if you ask (be ready to get a beer in a tea pot, or to be asked to say you brought it with you if someone asks you about it).
Alcohol is not sold in supermarkerts, for that you have to go to wine stores.
We mainly used public transport to travel around: bus and trains for long distances and tuktuks for shorter ones.
I never fully understood bus stops. There is a blue sign, but you can't find information about which lines stop there, so better ask around.
For each line, there are buses from the government (red ones) and private owned ones (blue). Usually the private ones drive like crazy, trying to overtake each other to arrive first to the stops to get more people (and therefore more money). All of them are colorful and have loud music, sometimes feels like a party. There are luxury buses too, more like mini vans. Their price its really fair, they have AC, and they are a calmer experience. I didn't learn exactly where they start from, but came across them a couple times, ask around. More about buses: there are express ones, with less stops, and normal ones. You don't have a chance of stopping an express outside a bus stop, but regular ones will usually pick you up if you make a sign to them.
Bus stations usually have timetables and clearly signed where the buses are going. If in doubt, ask a bus driver, they are the ones that know better. But don't trust blindly everything a tuktuk driver tells you, I had a couple of them telling me "a bus is not coming" while seeing it with my own eyes.
Reserved train tickets sell out really fast, if you plan all your vacation before going there, you may want to organize one, but don't expect to get a reserved seat when traveling spontaneously. There are always unreserved 2nd and 3rd class tickets sold on the same day. The difference between them is not much, and for the more touristic places 2nd class are sometimes even fuller. Another thing to keep in mind: in the time we went there, the trains in the direction Ella to Kandy where semi full, you could find at least a spot in the door when there were no seats available. But the ones we crossedt going in the other direction were completely packed.
Where to stay
New places are usually great, if something doesn't have a lot of reviews, go check it out! Our favourite places were one with a couple reviews online, and another where we were the first guests!
We booked our stays one or two days in advance, or asked when we were there, and never slept in the street. I was worried about it before arriving to Sri Lanka, but it worked out really fine.
You don't have to stick to the place where everyone is. We went to Trinco in January, when it is low season. We were lucky and the weather was (mostly) wonderful. If you are a party animal it will be boring, since a lot of places will be closed, but if not, it might be worth a try it. It is less full, you stop hearing "tuktuk?" all the time, places are cheaper and people are overall nicer. We event went to Pigeon island: the day we planned it got cancelled because of the weather and went the next day. After a bumple boat ride, we were almost alone there and got to see sharks even if the visibility was not optimal.