How to buy ram for laptop?

My laptop is Samsung NP350V4X.
Please don't suggest crucial scanner. (because
they don't sell ram in my country and they
suggested 1.35v ram but my pre installed ram is
1.5v)
So what should I see while buying ram? (like speed pins etc)

I could not find a downloadable manual for your laptop at Samsung, but it appears to use 204 pin DDR3 unbuffered non-ECC RAM. A maximum of 16 GB, with 2 available slots.

The choices from the Crucial configurator show either PC-12800 or PC-14900 speed. The former is DDR3-1600. The latter is DDR3-1833. Both shown are 1.35 volts as you say.

Can you buy Crucial RAM from any available dealer in your country, not from Crucial directly?

If not, I'd search for a source for RAM with the above specifications from a manufacturer such as Corsair, G Skill, or Kingston.

Either 1.5 volt or 1.35 volt. Probably DDR3-1600 rather than DDR3-1833. The 1600 should be a bit cheaper.

I'd trust the Crucial configurator when it says your laptop is compatible with 1.35 volt RAM. You say your existing RAM is 1.5 volt, so it should be fine too. Just go with one or the other.

I wouldn't be particularly concerned with timings (CAS latency).

Here is a list of what appears to be compatible RAM sold by Newegg from several manufacturers. Look for these model numbers from your dealers. These are all 8 GB kits (2 sticks of 4 GB each).

Newegg.com - Computer Hardware, Memory, Laptop Memory, G.SKILL, Corsair, Kingston Technology Corp., Newegg, 1.5V, 204-Pin DDR3 SO-DIMM, 8GB (2 x 4GB)...

But how can 1.35V work with 1.5V.
I mean it doesn't feel right still thanks. But i would still like to get more advice.

You have 1.5 volt now.

If you are going to keep that stick, then buy another 1.5 volt stick.

If you are not going to keep that 1.5 volt stick, then buy either 1.5 or 1.35 volt sticks to replace it.

You didn't bother to tell us what your intentions are for the existing 1.5 volt stick.