Before you anxious and you let your heart rate pound with excitment for the unknown of what this casting could lead too: here are a few things to first consider.
When looking at the casting posted, whether it is a breakdown, on the Internet casting websites, on Craigslist, -where-ever! Always. Always Google the production company, the brand, or photographer's name. It is best to find out who are the people who are running this job, casting, film, ect.
It is a good thing to: Find out a little info about the brand, person, company and it will give you a vibe for how this job would be for your resume and if the company, photographer, job seems quality.
Also there is no harm in replying and asking for more info,-which will tell you more about the job
Also if the name of the production team, photographer, product, isn't bluntly mentioned, then notice the email and the name attached to the dot com, -put the dot com name in your browser and research the brand and person who is posting the post...if it is some packaging company, looking for models this might seem odd but really production teams of all kinds need models, but still if you are not sure and feel it might be a scam then why not call the company and ask...are you currently looking for models, I saw a post and it lead me to your company....I am just curious if this is correct?
There are alot scams and jerks out there. So it is better to be careful, cautious and curious, along with ambitious!
It is great to self promote, but it means to also watch your back and be smart about your pusuits!