The Russian join is a very neat, effective way of joining yarn ends together to avoid lumpy knots in the fabric of your knitting or crochet. ChemKnits explains it clearly and patiently and then it's a case of practise, practise, practise. I try to avoid changing balls of yarn in the middle of a row and keep an eye on what is left so I don't do that. There are times when you are caught short and times where you just need to add a small amount of colour so knowing the Russian join and any other way of smoothly joining yarn is helpful. Everything you learn increases your flexibility and ideas.