Unfortunately the answer typically boils down to one of three things:
Spending less
Earning more
Inheriting money
In the absence of the third option, my wife and I (age 27 and 30) focused heavily on the first two. We live in a VHCOL city so we try to earn as much as possible. I earn $120K and she earns $325K with the possibility for substantial growth in the future.
We also live very lean. We purchased the smallest housing we could tolerate and get around by public transit. We make our own meals at home, and our one big extravagance is travel.
Her path has been straightforward but mine has been meandering. I have taken multiple six month breaks from work and changed careers entirely once already. My average annual income since I finished my undergraduate degree is $65K, but I’ve still managed to save and invest my way to about $250K.