So the common questions are,
How can I pay?
What currency is accepted?
What is the exchange rate like?
Where can I exchange money?
What tips should I leave?
So to go through these in detail
How can I pay?
What currency is accepted?The legal tender in Sri Lanka is the Sri Lankan Rupee, no other currency is accepted. The Sri Lankan Rupee like most other currencies has Notes and Coins, the smallest note is Rs10 and the largest Rs5000. You will need to get used to the different notes. Notes are available in the following Rs 10 , 20 , 50 , 100 , 200, 500 , 1000 , 2000, 5000. You are most likely to use notes more than you will use coins, as there are very little things you will be able to purchase with coins. A complete list of legal tender can be found here - http://www.cbsl.gov.lk/htm/english/06_cm/c_1.html#1 . This link will give you an idea of what each of the notes and coins look like. That said, the value is clearly marked, and all the value is written in English as well.
All notes and coins are issued by the central bank of Sri Lanka. Recently the bank issued a new series of Notes. These can be seen here - http://www.cbsl.gov.lk/htm/english/06_cm/c_4.html
What is the exchange rate like?Exchange rates can vary from time to time. As at the point of writing this article £1 gets you Rs.206 and $1 gets you Rs.126.
You can find the latest rates here - GBP to LKR or USD to LKR
What does £1 get you in Sri Lanka, well, you could buy your self a local meal, or in global terms you could get a burger at KFC , menu found here , or quite a few things from a local eatery. Due to the high exchange rates your buying power will be quite high. £1 can also get you a ticket on a bus to Kandy from Colombo.
A glass of Lion Larger at the Brewery By O in Colombo also costs around $1 (£0.80), the last time I went was around Rs 130. Where as a cocktail can cost around £3-£5 ($5-$8), Rs 650 - 750.
This said you will find that a typical meal can cost you between £5-7 (Rs 1000 - 1500 ) and if you want to splash out £5-15 (Rs 1000 - 3000 ) per person for a very decent meal, dependant on your choice of venue.
I hope that gives you some what of an idea, without going into too much detail.