Welding is an essential job and a difficult job if you are not skilled or if you are just starting out. Being able to run a straight line is an important part of welding as well, and learning how to go through and run a straight bead can make a huge difference in the overall finished product and how it looks when it is finished, master welding classes can help.
Running your first bead on the edge is a great way to help orient your rod when you are working and to help you keep your bead and your weld straight.
Using the toe of the previous weld if there is one, is also a great way to help you keep a straight line. You also want to keep a relatively consistent speed, you want to avoid running faster or slower as this is going to change the overall width of the weld and the bead.
You want to take the time to really pay attention to what you are doing, to make sure you are concentrating, and to take your time to make a clean and straight weld overall. Taking your time can make all the difference in the finished product.