Basically, the rule is that your first job after college should be with an employer that will sponsor your green card application. I knew that when I graduated and it was my number one criterion when looking for a job. Most of my foreign-born friends knew it too and they did the same. Most, but not all. The ones who didn't due to naivete, carelessness, or limited job opportunities ran into problems later. You have only 6 years on an H1B and time flies quickly. US society is in general very welcoming to immigrants, especially highly-skilled ones, so it's easy to forget that you are just a guest here subject to the vagaries of the system. Getting the green card should be the absolute priority when selecting an employer, no compromise.