Safety with a cordless saw is much the same as for one with a cord.
Wear safety glasses.
Use hearing protection (soft ear plugs or sound-reducing earmuffs)
In general, don't work with power equipment when you're alone.
Have first aid material handy. This isn't a joke. Look at all the carpenters with missing fingers!
Let no one stand in front of the saw.
Make sure the blade is firmly attached.
Support the material being cut on both sides of the cut.
Keep the space under the work clear, so you don't cut into your support.
Keep hands well away from the line being cut.
Do not force the saw through the work, let the blade do the cutting.