Watch the The Most Common Lick online guitar lesson by Jimmy Heffernan from Dobro Handbook
This is the most common lick ever played on the dobro - it's the first one I ever learned and I use it to this day!
We'll jazz up this lick later on in the course but for now, learn it as shown here. The lick is simple but there's a lot of technique you need to employ to make it sound clean and really good.
Take your time and don't rest until you have a solid grip on it. A lot of licks are based on this so this is a really good foundation to work on.