If you are visiting the any plant, where some alcoholic drinks are produced, then you should take care of following things.
Plan four to five stops
The big wineries used to have many spots to be visited and going for all of them means, making the trip hectic and tiresome. So, do not choose to see all the locations. Instead, make a list and chose four or five spots to visit. This will give you ample time to see and know about each place. 
Consider the entire travel time
From the beginning of the travel to the end, make a checkpoint, how much time it is going to take to complete the whole trip. It is important to gauge this time, whether it is a group winery tours or a single one. The reason for the same is that you will not get over tired and will have some time for shopping as well. The wineries used to have gift shops; from here you can purchase some bottle to present it to your loved ones.
Chose the travel month wisely
You can ask the wineries about which is the busiest month they have and they will tell you fall or summer. If you chose to visit the place during the peak season, then it is better to start a little earlier, this will save you from the afternoon rush. However, spring and winter seasons are considered as the off-season. If you are bound to visit this winery https://en.wikipedia.org/wiki/Winery in the peak season, then better to plan the trip in the off season. This will let you have more personal experience and also you will be able to enjoy more due to less people.
Do not forget to carry an empty box
Maybe you would not plan to buy bottle of wines, but when you taste it, you may develop an urge to have it. And if you will not have a box or a carry bag, then all that happen will is, your bottles of wine will roll back in the back of your vehicle and possibility of damage is also there. It happens too many. And what is the issue in carrying a bag. Even if you are not buying any wine bottle, it can be used to keep other stuffs like a bottle of water, some snacks in it. So, if you have not taken a trip to a winery till date, then go for it and to have great experience to book the group winery tours of the Barossa valley.