I'm new to this and have no pictures to show so I will try to make my description as clear as I am able.
I'm not sure where I learned this "how to" but I have been knitting since I was a teenager and I will be 57 in May. I had stopped for many years until the 1st yarn shop opened in my town. Anyway another story for another time.
The way I have found that I really like is this.. thread working yarn to a yarn needle. Use one that is a little pointer than the blunt ones and make a loop by running yarn on needle back thru the middle of strand
for about an inch but just pull end out and leave loop for now. Thread new yarn and run thru first loop then use the same procedure thru new yarn. once that is done tighten yarns together by 1st pulling on e3nd of old yarn to tighten the loop (you will have a short length to tip of yarn), then do the same with new yarn to tighten that loop. when both loops are tight, slide the bunched yarn down each side toward tip of old and new yarn then trim ends. If you twist the yarn a little you don't see the join.
Once in a great while a little of a tip comes out but is easily trimmed.
I hope that helps, but either way I'm glad I contributed. If I figure this out I will attempt to send some pics of what I have knitted recently.
Thanks Robin Jonson