During your trip to Sri Lanka it won't take you long to realise that the inhabitants are friendly and welcoming. You should also know that their lives are governed by rules of etiquette which need to be respected.
During your trip to Sri Lanka it won't take you too long to realise that here a warm welcome is not just a legend, it really exists. To say hello to locals join your hands together, smile, and say "Ayubowan". In fact you should smile at all times. The Sri Lankans are very calm, they never get annoyed in public and they smile whatever the situation. The instruction is the same for everyone, keep cool and keep face. It is always seen as rude to become annoyed in public.
You should be very careful about how you are dressed. Sri Lankans are very modest and to ensure you do not shock or offend them you should always be decently dressed. Be clean and avoid showing your arms and legs, especially if you are a woman. This is especially true on religious sites which won't let you enter if you are not dressed appropriately. Couples are always discreet. Open demonstrations of affection do not happen in this country where even holding hands in public is unusual.
After the years of conflict between the powers that be and the Tamil Tigers you are strongly advised NOT to give your opinion about politics.
Because you are a tourist you will always be approached by beggars or by children asking for money, sweets or pens. It's always difficult to know how you should behave in these situations. It is often difficult to resist, or to say no. It's not possible to tell you the ideal way to behave. You must do as you feel best, whilst telling yourself that it is always preferable not to encourage begging. If you want to give, then choose local charities which are working in the area, or hospitals and clinics which need medicine. Don't think you can only give money. If you have time or a genuine skill to share, that can be a real benefit.