Generic Ritalin SR questions | ADHD Information

I am taking this medication (just started this morning).  I was quite anxious about it as it took me 9 months to finally decide to try medication.  But I have a couple of questions that maybe you all can answer and save me a call to the pharmacist.

How long do effects last?  I mean you take the pill in the morning but by what time of day do they start to wear off?

Also, I read somewhere that you should avoid citrus fruits (oranges in particular).  Why? And are there other foods to avoid?

Thanks.