when a newb find a bug it usually means he is the bug himself.http://www.catb.org/esr/faqs/smart-ques ... 4142381904
also bug report should include technical details to make it reproducible by devs, or at least should try to.
For both those reasons the first thing to do when "thinking you find a bug" would be hitting forum/chat
There you would ask people to reproduce it.
1: People would try it and say "Yeah! that thing happens, really..." - good. You got an easy to reproduce bug, go to bugtracker ( if it would accept login/password from forum
2: People would say "you are fool, OpenTTD program acts like it should and you are doing this and that wrong" - good. You may not wait for the fixed release and fix your ways right now, also you did not polluted the tracker with invalid issues.
3: People would say "no, we tried what you describe and it did not happen" - there it goes... interesting? tedious? You and many people in forum would have to pinpoint the required condition for reproducing. After many boring/fascinating iteration you would end with either #1 or #2 and then you would have register the issue.
Before that going "directly to tracker" is preliminary to say the best.