LS TTL & HC CMOS ICs make compatible

I am using both LS & HC ICs in a single application.
As Rogs (member-'all about circuits') pointed out, the output is not getting due to type mismatch.
But in our local market only 74126, 7474,7447 LS versions are only avail.
Does there exist any methods to make compatible both versions without any problems ?

Can you get 74HCT parts? They are compatible with 74LS.