and now from a grandchild's perspective . . .

the best thing that grandparents can do is model christian love
and all that means 

individually, 

grandmothers, ALWAYS take your side...regardless...any time...

grandfathers always are the ones that can help you break those little rules your parents put in place just because...ice cream just before bed time, helping light the fire, learning to use the riding lawn mower when you can just touch the controls, getting the car when your parents don't think you need it.

Always volunteer for bathtime when they are young.  There is no such thing as too much water out of the tub or too much splashing.  Both make for more laughter, which makes for more splashing.

Baths are great for dealing with a fussy baby.  Get the water temp right and plunk them in (face up), then see above.

Let them see your Faith.

Love them unconditionally.
Let them know you are there for them if they need to talk about anything.
Remember you are the grandparents not The Parent (so you get to have more fun).

Brush up on Math and English, Science and History etc. because you may be doing a lot of projects.
Take time to go fishing and baking.
Travel with them, teach them how beautiful everywhere is, not just here.

Special holidays where their parents have to work become “cookie day”. They know they’ll never be chastised  for plunging their index finger into the uncooked dough since you also are willing to join them.

Go to the local tobogganing hill and seat them at the front. Be brave. Tell them this is a lesson and they have to learn that there are ups and downs. The pleasure of downhill means the struggle to going to the top.

Have an open “grandparent line” which means either through the antiquated telephone or Skype be there for them. Learn of what they did at school, their fears, surprises and later maybe about who walked them home. You have to earn this right by taking time for them and give them your sole attention when you are together.

Chauffeur at demand is their expectation when they just have to go to a friends’ in a neighbouring town since they are having fun and have so much to tell each other that they didn’t have time for at school.

Offer to be there if things aren’t going well and call you to come home at any time. This is an important offer especially for teenagers.

As you notice, these things don’t cost anything but the most costly thing one seems to have today – time. It is an investment for their future.

You don’t have to spoil grandkids with materialistic things and you can’t spoil them with too much LOVE.

The payment comes later in life when they repeat when leaving “I love you, Grandma or Greandpa!”