Checking their steam profile is an easy thing you can do to avoid being scammed.

• Check if their profile is private
  I'd recommend not accepting people with a private profile. People who have their profile on private are usually phishers or scammers.
  
  
• Check for bans
  On the right side of their steam profile, check if he has a 'trade ban' or if he is on 'trade probation' or 'under supervision'. If he does have any of these bans I wouldn't recommend you to add him.
  
  
• Check how old his account is
  You can check how old someone's account is by going to their profile. Then clicking on "Badges" on the right. It will open a new page with badges. Look for the badge 'Years of Service' and click on it. It will open the badge information and show 'Member since ...'.
  
  If the person has no 'years of service' badge, it means his account is less than 1 year old.
  If someone has a new account doesn't mean he's a scammer. Just be on high alert.
  You can also check how old someone's account is by checking their steamrep (see the steamrep section later in this guide).

Steamrep[steamrep.com] is a non-profit site that partners with community administrators to improve the safety of game-related trading.
To check someone's steamrep you first have to go his profile and copy his URL. (You can do this by selecting it with your mouse and pressing CTRL+C)


Once you have his URL you go to http://steamrep.com. paste (CTRL+V) his URL under 'Check reputation status for a Steam user' and then press 'Search'.


The steamrep page will show information about this user. On the left of the page it shows the user his "Reputation Status".

For more information check Steamrep's FAQ.[forums.steamrep.com]

Phishers are usually bots that add you and then send you a message containing a link., When you visit this link it will immediately download a virus.
Phishers usually use website links that are similar to steam's real website. websites like: steamcomnunity, steamcomuniity or staemcommunity. Messages using these websites usually look like this:

Hi. My friend can't add you as a friend, he receives an error "exceeded limit adding friends for 1 day" - but he wants to trade with you. Please add him. [phisher link]

It's also common for them to send you link that looks like it contains an image (by ending the page url in something like .png), but in reality it's a virus.

Hi mate! I want to trade with you, My trade offer is shown in this image. [phisher link]

Tip: Don't trust any links sent by other users unless you are sure you can trust them.

A user tells you they will trade you a specific item, and the item they put in the trade box looks like the item, but isn’t as valuable as the original offer.
Tip: Double check the contents of all trades before accepting.

A user offers you a specific quality item, but the item in the trade box is of a lower quality. Often the item switch is made in a counter-offer.
Tip: Double check the contents of all trades before accepting and pay special attention to the item quality.
With Item quality is meant the quality of skins (factory new, minimal wear, etc)

A user offers a trade that includes a lot of your low value items (cards, crates, etc.), but also includes a high value item hidden somewhere in the middle.
Tip: Double check the contents of all trades before accepting.

A user spams out hundreds of trade offers requesting high value items for nothing in return in hopes that you mis-click and accept the offer.
Tip: Decline all offers that don't appear to be a fair trade, even if the items requested are of low value.

Enhanced Steam is an Extension for Google Chrome, Opera and Mozilla Firefox that adds many new features to the Steam website.
Enhanced Steam will add a direct link to the person's Steamrep page. Also will it show their steamrep status on their profile.
Enhanced Steam comes with many more features. to view those features, or to download Enhanced Steam; go to their website: Here.[www.enhancedsteam.com]

You can always comment on this guide, or add me if:

• You have any further questions or suggestions.
  
• You think I forgot to add something.
  
• I used one of the images you own and you want me to remove them.

Information is gathered from the steamrep website and forums[steamrep.com], and the enhanced steam website[www.enhancedsteam.com].