AWS IAM user creation and access

IAM user set up can be found here:
http://docs.aws.amazon.com/IAM/latest/UserGuide/Using_SettingUpUser.html

Give them 'Power User' if they need to create instances and fully utilize AWS services.

They will use a different URL (not aws.amazon.com) then you use to access your account.  More here:
http://docs.aws.amazon.com/IAM/latest/UserGuide/WhatUsersNeedToKnow.html

AWS getting started with groups and users

A common question is when first setting up and AWS environment is how to prevent developers, OS administrators, DBAs, architectures and all the different roles you may have in your organization from having the correct privileges.  You use IAM group and users.  You would create a developer group.  Ignore roles to start with as these are for AWS services to access other services  (example: EC2 accessing S3) and cross account access.  Then add policies to the group (use policy generator or select a template). Then add each developer as individual users and adding them to the developer group.

Good resource for all of your questions….You can explicitly manage roles and policy

http://docs.aws.amazon.com/IAM/latest/UserGuide/IAMBestPractices.html

http://docs.aws.amazon.com/IAM/latest/UserGuide/cross-acct-access-walkthrough-creategroup.html

Nice blog entry here:
https://forums.aws.amazon.com/message.jspa?messageID=197920