Check with HR, as they may have a specific policy regarding notice. If there is no policy, the traditional guideline is at least 2 weeks' notice.
You don't have to follow HR's policy or give notice...but keep in mind that not doing so increases your risk of being labelled "Do Not Rehire", that you'll be given a bad reference or have a hard time getting a good (or any) reference from anyone, and/or that other employers will find out you left without notice when they call to verify your employment...and, yes, it's perfectly legal for them to tell future employers you left without proper notice if it's true.
Some here may say you don't need to give notice as an employer won't often give you notice when they terminate you. I suppose that's true...but remember, it's not 2004 anymore--it's definitely an employer's market now, and there's a real risk to your next job hunt if you decide to leave without notice. Keep that in mind when deciding.
Thank you for the advice! I called HR and they said 2 weeks. I will be giving a little more than 3 weeks (just cuz I know when I want to go already and also its more time for them to take care of my paperwork? dont know if this is a smart move...)
Anyway, would it be better to tell my manager beforehand via email that I will be resigning and then give her the letter, OR just give her my letter of resignation when I see her? I just dont want to surprise her...
When I gave notice at my last position, I called a meeting with the DON and administrator and gave them my written notice as part of my meeting with them, so I kinda did both. Of course, I had mentioned for months that I may leave due to personal circumstances, so they weren't surprised.