It varies, it can be stressful sometimes if you bought at a bad website.
It is much better to buy tickets online. You are guaranteed to be charged about fifty dollars more at the gate.
http://www.bestticketshere.com/ appears to specialize in discounted Disneyland tickets, though they only offer tickets for both parks, not single-park tickets. Their tickets come with a money-back guarantee, and accept all major credit cards.
Disneyland.com is a good place to buy Disneyland tickets, you can also buy them at the kiosks in front of the gates at the Disneyland Resort.
Purchasing tickets online is safe. There are many reputable businesses that process purchases through a safe and secure site and most will compare their price with other known companies.
Adventure Island is not free. You have to buy Disneyland park hopper tickets, then it free. If you buy Disneyland tickets you can only choose one theme park and stay there for the rest of the day.
Check the seller's feedback rating. I get my NFL tickets online from Vertex Tickets for a good selection and seating options. VertexTickets.com
There are various sites that offer Disneyland discounts. Welcometosocal is one and cheap-disneyland-tickets is another. If one buys tickets from ARES travel (arestravel) they are able to offer a small discount. All of these sites are dot-com sites.
Yes, you can buy sporting event tickets online. You can buy these tickets from Ticket Master or Stub Hub.
You can buy these online though a travel broker such as expedia.com. They have great deals and you will be happy you used to book your deal.
No. One Disneyland ticket is access to EVERYTHING inside the resort.
Yes, you can buy Broadway tickets online. You can get them at Ticket Master or from Telecharge.
Go to family-fun-favourites.com they have the best deals on tickets to Disneyland. Do NOT buy the tickets at the park itself as this is the most expensive and time consuming. Pre-book your tickets online to avoid queues and if your willing to pay more I'd advise you to throw in Fast Track as you can skip the queues for the rides(which means less complaining kids!)