The most effective way is attending in-school job fairs

Every semester those biggies in need of workforces will come to your school to host such fairs. They are aware of your lacking experience and willing to open up entry level positions for you. Your starting point would be your school career development center.

Some websites may be informational, you can try, but most likely those openings are for experienced ones. Those websites include, not limit to:

Dice.com
Headhunter.com
Dic