So you have a new rat, congRATulations!! Everyone is home and in their new cage. You watch them as they run from corner to corner and munch on the new foods and treats you left them. 

You go ahead and decide to make a move to get better acquainted with your new furry friend. Open the cage speak softly to them and reach in to say "hello" only to have them run like made to whatever corner they can and hide from you. Its disheartening!

Rats are very inquisitive and really can feel our emotions so easily. Your uneasy and so are they, your scared and they may be too. Even the most socialized rat may need to help you understand whats best for them. 

If a rat tends to be a bit more shy then you would like you can go back to square one with them. Not all rats respond to socialization the same, You being their new owner will figure that out. 

A fearful rat will normally scream and or fear poo when you are holding it. DO not chaise it around the cage and try and grab it, that is just going to make things much worse. Never put items over your hands, no oven sits, gloves or use a towel to chaise your buddy. Never ever grab the rat's tail to catch them. They fear being chased - Patience and persistence wins over all.

Rats do not bite, they will play nip on occasion normally inviting you to play! Baby rats sometimes haven't been taught what is too hard when playing.  If a rat bites it's going to be bad and I can honestly say I have only been fear bit maybe 5 times in my 20+ years of handling rats.

I suggest removing a lot of hides, things they can dart under and behind and just hide from you. You can always put them in and out as well for specific times of the day/night. They can be forced a little to learn your homes noises and smells. 

Do not make loud kissy noises to your rats, they rarely care for that noise. I tend to make a click sound here that  all my rats even babies have learned to respond to. 

Grab a yummy babyfood or yogurt and spoon (may need to try a few different ones) pick a time of the day that works for you and stick to that time each day. Do not free feed your rat. Sit/stand at the cage door talk to your babies, and open the door with spoon and baby food in hand dip the spoon into the food and offer it in hand to your little ones. They will come lick out of the spoon. Do not try and touch them do not move too much let them just lick their treat from the spoon. After you are done "socializing" with them for a few you can them give them their regular food for the day.

Once the rats are coming and running for your "spoon of goodies" every time you open the cage then you can move the spoon on top your hand so they are essentially eaten out of your hand. Next, require they let you pet them while they enjoy their treat. They will stand on your hand and lick the goods. Gradually (may take several days) lead the rats to your arm eating from their spoon and you're holding them. Eventually they will be running to you every time you walk towards the cage, especially if you have a treat! 

Once rats are used to a treat time when you arrive you can offer a cheerio as a hello every time you open up the cage to say hi to your new friend.

Once they trust that you are not going to grab their tail, squeeze them or turn them over on their backs they will enjoy being with you more and more. Furthermore you will learn each of their personalities and funny antics. Each rat is different and some may take more coaxing then others. Rats however, learn form other rats so if you have a social rat in your group of rats then they will eventually, Monkey see monkey do! :P 

When you are able to hold carry and play with the rats I suggest playing with them away from the cage.A lot of times they will cling to their safety zone.You want them to bond with you. I suggest maybe a dry bathtub. This lets them crawl all over you while being confined. Does have to be for too long but it helps them see your a friend.

Good luck!