Newly Diagnosed

My 59 year old husband has finally been diagnosed with severe ADHD.  He has talked about getting help for our entire marriage, but never followed through until now.  He has been prescribed the generic form of Ritalin (10mg), two to four times per day.  He is currently taking a pill in the morning and another one later in the afternoon.  Does anyone have any advice on what I can expect as far as side effects and pros and cons of him taking Ritalin?  Thanks.