How do you properly sear a sausage?
If you are frying sausages on a hot pan then it's very hard to brown them on all sides for a couple of reasons:


the curved shape will cause it to flop along the curve, they are hard to stand up
if you do get them stood up only the small area touching the pan will get color


So you are frying on a flat pan you can spend a lot of time messing around trying to get color on the sausages, I personally don't think it's worth the effort and just fry them on the sides they rest on. However, I rarely cook sausages this way, I usually use my broiler/grill. The advantages to this are that the sausages get more evenly browned and that the wire rack I makes it easier to stand the sausages up or down as opposed to side to side. 

If you do plan to use a frying pan you could get one with ribs in it which will help position the sausages.