Currently our web servers have 2 nameservers (as all do at least)

I set both ns1 and ns2 the same as each other, and in the registrar side I just point ns1 as primary, ns2 as the secondary

Is that the correct way?

I read that the 2nd one usually does reverse dns or something.. or is my understanding on this matter totally screwed?

also how do i set it such that it will always use ns1.. then refer to ns2 only when ns1 is down? or is there a need?

Yes, that will work..
Sometimes the dns server wil make a warning message loading your zone info if there are 2 identical records.. but it's not fatal.
A better idea is to have two different url names and the same ip address..

And best is a separate 2nd dns server..

There is no technical reason for having two..
It's just a policy based on the fact that the internet isn't a 100% up medium, so one of the dns servers will be unavailable sometime.. and coz dns is so vital it's a good policy.

Reverse dns needs to be handled by your ISP. It is their number block so their responsibility to show correct reverse records.

oh sorry i haven't been cleared

my 2 dns servers, are 2 separate physical servers

what i mean the same as each other, is the settings for zone files

is there a need to specify in the zone files which is secondary which is primary?

No need..
The dns server will usually rotate the list.
Some even determine the order by the source ip address of the pc requesting the info..

Slave and Master exist for dns servers to allow changes on the Master to be propogated to the slave servers when a zone is refreshed..