I am trying to decorate a cake using the Wilton tip #250---the Christmas Tree one. They are not coming out looking like a Christmas tree at all. Do you have any suggestions on how to use it correctly? TIA.

I would imagine I'm too late, but...
That's the one that makes little horizontal lines. If it's coming out like a blob, your icing is too soft (thin) or you are squeezing too much out. It takes very little pressure to make it work right.