When you turn make sure your working yarn is coming from your left needle. When you start to knit you can tell if it's going to join.
I replied on my phone at my social knitting group so probably wasn't too thorough here... Anyway...You can place a marker like Salmonac said and another thing you can do is place removable marker on the front side so you'll know which is which. Just pretend you're using two separate needles and turn and knit back on the same needle. Just watch your working yarn.