Actions such as setting the default access level
'restrict default ignore'

Alowing access from loopback:
restrict 127.0.0.1

The Client Network Access levels:
restrict 10.10.10.0 mask 255.255.255.0 notrust nomodify notrap

Then define Timeservers by first defining access levels and then defining the timeserver:

restrict 192.43.244.18 mask 255.255.255.255 nomodify notrap noquery
server 192.43.244.18
restrict 18.145.0.30 mask 255.255.255.255 nomodify notrap noquery
server 18.145.0.30
restrict 192.5.41.40 mask 255.255.255.255 nomodify notrap noquery

Just a few suggestions....