Choose your claim.
There’s a lot of BD classes, as well as some Neutral classes you can claim. You should generally prepare 2 claims. One that fits your class type and one that doesn’t.
Claiming out of type, makes you less likely to be narrowed down for being starting evil, but it runs the risk of having to guess ability results and being found by a Princess.
Having 2 claims ready, allows you to safely pick the better option without having to panic and scramble for better logs.
Write your logs.
You have to fake your abilities in a realistic way. Claiming to, for example, Flirt and already outed player will make people suspicious of you, so you should claim your abilities in a way that a real Blue Dragon would.
Writing your logs in a simple and easy to read way might also help you avoid suspicion, due to the other players just skimming though them.
This is the most important step, but underused by many. You need to sound, breathe, and look BD to fool those who are after you.
In this step I would include: outing yourself at the proper time, posting your logs or action feedback when they are needed, voting in a manner that a BD player would, amongst others.
If you want for your claim to be believable, you need to play actively, rather than passively. This would include, for example, saying that someone is confirmed and posting your fake logs that confirm that player, rather than wait until someone tries to get you to post those.
Try talking more.