In Scotland, you don't generally order at your table unless you're going to eat - and even then you usually ask for your drinks at the bar and take them to your table yourself. You usually pay straight away although again, if food is involved, you might be given a bill when you've finished eating. Licensing laws vary from place to place - they're usually posted somewhere prominent and hours tend to be longer on Friday and Saturday nights. These can vary again according to the time of year - summer or Hogmanay usually means longer opening hours.
Some places have rules about children visiting after certain times or sitting in certain areas.
Don't drink and drive - sounds obvious but the laws are strictly adhered to and at best you'll lose your licence if you try and wing it and get caught. Pubs can vary and you might find anything from an appalling dive to an establishment that is the heart and soul of a community.