Here are some advises for newbies.
1. Never deal with anyone before checking his trust page. (Enter the profile and push the button Trust ) You will see two types of feedbacks. Trusted and Untrusted. Trusted feedbacks are visible for everyone by default unless you make changes in your trust settings. Untrusted feedback's can be seen if you push the button Show ratings. Take into consideration that untrusted feedback's can be totally inaccurate.
2. Avoid dealing with newbies, especially those that are offering BTC Buy/Sell deals.
3. Avoid BTC Buy/Sell deals via PayPal (Can be charged back)
4. If you are planing to invest in any project, check very carefully the whitepaper and team members. Sometimes scammers are using stolen pictures and plagiarized whitepapers. Use online plagiarism checking tools and check team photos via google or yandex. Also check the OP's trust page. Please take into consideration that some projects are using so called bump service. (A lot of newbie profiles are posting positive comments in the thread.) That is a clear sign that the project is a potential scam
5. For any deal always use an escrow service even if it is a small amount of money. Reputable escrows can be found here.
https://bitcointalksearch.org/topic/recommended-bitcointalk-escrow-services-2439910
6. Always ask for previous works links if you are hiring someone for any work. Avoid hiring newbies.
7. Avoid deals that are too good to be true. Especially those that are offering huge profits.
8. Avoid buying or selling accounts. (Your profile will receive negative red trust score)
9. Avoid participating in any bounty campaign managed by unknown or newbie profile. Also avoid so called airdrops. Reputable bounty managers can be found here. Check the poll https://bitcointalk.org/index.php?topic=5032713.20
10. If you do not understand something, contact the forum moderator or any high ranked reputable member with positive green trust.
11. Do not randomly click on any link: Many links lead you to scam websites or download viruses to your computer.
12. Do not download any untrustworthy wallets/apps: This includes closed source and the new wallets/apps "Hosting on Github will not change anything."
13. If someone will ask you to deposit any amount for participating in any project or if someone is asking you to pay for receiving bounty tokens or coins, avoid that requests, because there is a big chance that you will be scammed.
Please add any info if I missed something.