Go online and find the cracks/methods to open them.
Or start with easy numbers - mainly related to football... 1966, 1973.
Then go with war types - 1916/1918.. 39-45 etc.
1234
4321
1111
2222
3333
4444
1122
2244
1144
2211
and so on...
Feel for the movement of the pieces inside.
Use intuition. Try car number plate numbers/house numbers and combinations. Find out when various members of the family were born/died, compute compute compute.