Disclaimer: Im still learning a lot myself, but have been working with lipos for several years. These are the things I have learned. So others may have more.

Do:
- For best performance and life of the battery, always balance charge (as opposed to not using the balancing leads to charge).
- Always charge at recommend charge rate. Usually 1 C (5400 mah = 5.4amps). I realize your charger only goes to 3 Amps, just do the best you can with what you have.
- Always bring your packs back up to a storage voltage after you are done using them for the day. About 3.85v per cell, or 7.7v for the pack. With out a voltage meter on that charger it will be harder to get exactly to that. But any charge below full discharged state will be huge. Probably takes a bit more then two hours to charge your batteries on that charger. Maybe time it for about an hour on 3amps. Or turn it down to 1 amp for 2hrs. Lower amperage can help to stabilize the cells for extended periods in storage.
-Use a fireproof lipo bag if you want the highest possible safety. Chances are low that it will cause a fire, but I have seen more then one catch on fire and I like my house.

Dont:
-Run without lipo cutoff set on your ESC (check instructions, most have it on by default)
-Never discharge your pack below the lipo cutoff voltage as this can damage and ruin your batteries. If the car starts to loose power, stop driving.
-Leave your batteries fully charged for an extended period (more then 24hrs). Try to use them ASAP after charged or discharge them to a lower voltage if you know you wont be using them to help extend the life.
-use a battery that has swollen cells. Typically a sign that your cells are damaged and charging them can start fires. Some people will continue to use it if its a little "puffed" as the anode will naturally decompose with age, producing oxygen, but any significant puffage and the cell should be avoided.
-Submerge in water

These are some things I have learned. Hope they help