The most common discourse markers are:
'You know' is used to share knowledge about something.
- "You know, this candy isn't even vegetarian."
'Actually' is used to contradict something that's been said, or to say something in another way.
- "Actually, that's not true at all."
'Mind you' is used to mean something like 'we should also remember that'.
- "We could hold the party outdoors this year. Mind you, last year it rained all day."
As I was saying…
'As I was saying' is used to pick up a previously started topic, perhaps after being distracted or discussing something else.
- "...As I was saying, I'm not sure what's going on with the construction works outside."
Come to think of it
'Come to think of it' is used to indicate that the speaker has suddenly realised something.
- "Come to think of it, I don't think I locked the front door this morning."
'So basically' is used to summarise previously made statements.
- "I was too ill to go to work today and now my car's broken down. So basically, today's not going well."
'Anyway' is used to change the topic of conversation.
- "I really liked that book! Anyway, what shall we have for dinner?"
By the way
'By the way' also changes the topic, but usually as a temporary interjection in the conversation or for a less important matter.
"We definitely need to work harder to pass this biology test. By the way, did Joe get back to you about his party?"
'Well' is used to show that we are thinking about our response, or to indicate that our response might be unexpected.
- "Well, I'm not sure about that right now."
- "Well, actually I didn't really enjoy it."
'Right' can be used to begin a conversation or to indicate agreement or understanding.
- "Right, let's get this meeting started."