A lot depends on the connection to the rest of the floor plan, the front elevation of the garage relative to the home front and what your overall neighborhood value is.

If you are in a high end area, you must do it properly by raising the floor, opening a wall, replacing the garage with a freestanding garage. If you are in a mid-priced area, you may want to convert without converting at all - so the next person can use it for a garage again. A glass garage door may do it for you.

Or, if your neighborhood is an entry level neighborhood for first time buyers, you may be able to incorporate a cool mid century carport to replace it, and even design a side yard patio that gives it full design functionality. The garage may be the largest area to do a new cool space in . . Is this the largest area contiguous to the kitchen that offers an opportunity for the modern great room you envision?

to answer your question for you - how about a front of the house photo, and a sketch of the overall house floor plan . . . you may want to tell us more about the goal - are your kids taking over the house and you need a second space? Do you want more entertaining area to upgrade the house and move up, or are you happy to make it work for you and don't care about resale too much.
Hope these questions give you some ideas all on their own .. .post photos and we can help more.

The overall goal is to have more bedrooms and a play/family room. We currently have 3 bedroom for a 5 member family. We frequently also have company so we need extra bedrooms. Our current Garage is 30x 24.

I am currently working on a job like this. @libradesigneye covered a lot of the same things this couple did. They had the floor raised to the level of the kitchen, had the concrete insulated with spray foam and drywall installed. More electrical was added for lighting and appliances. They were also adding a small kitchen, as they have nine children and family gatherings are large. They also had the garage finished for overflow seating.

Can you sketch the rooms that border the garage back to the front door and take a photo of it, upload it? You might add one additional bedroom that can double as guest room - one child knowing they must share with a sibling during company visits. Or keep it a guest room until one of the kids reach 12 -13 - depending on the ages and sexes, a sleeping room full of bunks and a playroom in the existing bedrooms may work just as well for a few years, to keep the guest room open. If you begin by raising the floor level with the kitchen, and opening the new space to the kitchen and informal dining with a longer header, so you don't sacrifice space within the garage for circulation, there may be another entrance to the new bedroom from a different direction. 24 x 18 is a nice family room size, selecting the sidewall that offers an opportunity for large glass doors, add a skylight. That leaves 12 x 18 for a bedroom and alcove entrance plus 6 additional feet a generous sized closet and kick off additional storage / pantry for the kitchen. Post an exterior photo too and we'll offer style specifics for your situation.