Japan is a country that highly values courtesy and hospitality. The etiquette for sake drinking is also based on this set of values. However, these manners are by no means formal. Take them as hints for drinking sake in a more appropriate way.
Pour with both hands by holding the tokkuri in your right hand and supporting the bottom with your left hand. When pouring for someone on your right side, do not turn your right wrist over to pour. Your right hand will be facing down and that is considered poor manners.
Hold the cup lightly in one hand, and support the bottom with the other hand. When the sake is poured, take a small sip before putting the cup on the table. If your companion's cup is empty, offer to pour sake for them in return.
Pouring and receiving sake while spending time with someone is a great way to enjoy delicious sake together, and these become important moments for developing friendship.