Do you have to make reservations for olive garden ? and if so, how does that work ?

i heard they work on a first come, first serve basis . this makes me nervous because i wanted me & my friends to go out for my birthday . there will be around 5-10 people depending on who can come . so is it a bad idea to just all go together & see if there is a table, or do you think it might be full ? im going on a saturday or friday .