If its your booking in appt it will take approx 1hr. They will talk to you about yours and your partners health. Ask you questions on immediate families health, and any hereditary conditions.
They will take some blood to test for lots of different things (blood type, STDs, etc, all standard testing), do a urine test, and take your blood pressure. They will check height and weight and BMI.
They will talk to you to try and determine mental health, if your in an abusive relationship, how you're feeling about the pregnancy, etc.
They will take dates and give you a rough due date, but the 12 week scan will give a more accurate date (but then babies come when they want!).
It's all really relaxed, and just a chilled chat really. From that you get your green notes that they add to everytime you see them or have a scan.
Provided everything in straightforward and you get no issues you only get a 12w and 20w scan on NHS. (I got a cheeky extra one last time as at my '12w' I was actually only 11w so got to go back)
Hope that helps x