Look for glass on glass joints, as these ensure you have a closed system for smoke filtration.
Air mixed with smoke in the bong prior to inhalation can lead to staleness of smoke.
Joint locks, plastic clips, are used to keep things locked in so nothing
falls out and breaks during your bong rip(downstems, converters,
ashcatchers, carbon filters, etc.)
Cross breathing is an essential part of bong rips, making any bong much less daunting:
start with clean bong for best taste(mold grows in dirty bongs if left for too long)
Exhale air at start,
place mouth on bong,
light bowl briefly(to prevent scorching and destruction of THC),
draw air through bong slowly at first, cherry-ing(burning) the bowl.
once all smoke from bowl(or what you think you can take) is in bong, breathe in through nose
Exhale deeply through nose
Pull bowl and inhale smoke with mouth, mixing air through sides of mouth if too intense
Repeat cross breathing method for as long as you wish before clearing bong by pulling the bowl.
This ensures that you won't be left the end of a bong rip with hot smoke in the back of your throat, as you'll have enough lung space to breath more air in.