Roland's sword and buckler DVD introduces the concept of Strength and Weakness in balance. I think that basic tactics for sword and buckler involve trying to present your strength in balance to your opponent's weakness while avoiding his strength in balance. I notice that when you retreat from an engagement you go straight backwards and this means you're on the back foot facing his strength in balance - not good. If the engagement's not going your way try to 'flee to the side' and not backwards.
You didn't mention which sword and buckler system you're studying. You tend to keep the buckler quite low, almost waist height. I've been looking into MS I.33 and always try to maintain an appropriate forward lean (while keeping my weight evenly distributed between the feet - means the bottom sticks out a little) and I keep the buckler up at shoulder height. This way the lean makes the head the only viable target while the buckler stays high to protect the head.
Bon Accord Historical Fencers
"He (Liechtenauer) also means that you should not step straight in with the blows, but from the side at an angle so that you come in from the side where you can reach him easier than from the front" ~ Dobringer