On a daily basis - Make arrangements to spend a specific amount of time with each child.  It can be from 30 minutes to an hour or more.

On a weekly basis - Scheduled a date.  You can go to inexpensive restaurants, go for a walk, local event etc.

Play board games.

Teach them to love reading by reading to them every night.  For younger children use picture books.

Do chores and projects with them (building anything, hobbies etc.)

Play ball ( use a ball made of soft material to play with smaller children or indoor).