It’s an honour to be asked to do something in the service and we like to honour everyone, so you may well be asked.  This might mean reading the blessings before and after a section of Torah, lifting the scroll, opening the ark, or carrying the scroll.  You will be asked in advance if you want to read and interpret Haftarah, and if you have a Yahrzeit (anniversary of a loved one’s death), you will be invited for an Aliyah (reading the blessings).  And if you want to read a bit of the service, you only have to ask (in advance!).  It’s fine to say no if you are asked to do something, but we are all equally special, so we do like to involve people if we can.