The definition of Quality Post is subjective

One member may find your post as "quality post" then will give you a merit while other members may just engage you with a discussion without giving any merit.  Hence, I would like to suggest that just make it a habit to post something substantial and always (yes, always) be mindful of the rules of the forum.  Prevent yourself to be part of the ignored list of the merit sources.

Start Small

Just start small.  You can start on the things that you know or your experiences that you want to share.  I know that being a newbie, it feels like we cannot contribute anything in the forum because we have just little knowledge compare to the veterans.  However, I think some members would like to hear your stories of success, failures, learning, and not learning, and the like.  You can also post topic that interests you, in that way you can provide good insights by using your passion on the subject as the motivation/fuel to make a good post.

Start with "Beginners & Help" Category

You can start posting in the Beginners & Help category for you to ask questions and to be familiar with the forum.  It is advisable also that the target audience of your first posts are newbies (in relation with the previous point "Start Small").

Read. Read. Read

Try using the "search" bar if you want to learn certain topics.  It is really helpful (believe me).  By reading you will now the unspoken rules of the forum (what attitudes are frowned upon and what attitudes are highly encouraged).