Well where do you start ! Beach shacks - one of the main attractions for Goa. They are found all along the coastal belt of all resorts, so if you go south or north you have somewhere to stay for the day if you wish.
Constructed out of poles and palm leave roofs and most done in a very tidy fashion, you will find are mostly owned by locals.
All shacks have tables and chairs, a lot now going for a mix of cane with cushions and plastic chairs (wish people with wet swimwear would use the plastic ones !) Great food is cooked in kitchens attached to the rear of these, food quite often can be better than restaurants and menus getting bigger each season.
All will have ice boxes to keep those beers cold, and quite a few have fridges. Others have pool tables and dart boards, along with music systems.
Don't think there are many left now that don't have toilets attatched to them ? Most are kept clean and are nearly all flushable. Other shacks you may come across have showers as well, so no need to leave the beach all day !
Sunbeds are also at the front of all shacks and owned by the shack as well - some ask for a payment others don't.
Which to use ? your choice ! wander to the beach from your hotel and just go in one, if you don't like it for any reason, just move on to another - give as many a try as possible when walking up and down the beach (hic-hic !!)
Tips - again it's up to you and what you think the food/drink/service was like, they have all made decent money so don't go over board - if you choose one you think you will go to every day, tip small each day (round your bill up) and leave a bigger amount on your last day - up to you to decide that one.
All what you order will be added to a bill and presented when you leave. The lads in all shacks will look after you for all your needs, and quite happy to arrange trips/taxis/phones etc.. - anything really
Hope you enjoy yourself !