I,m going to let my property out privately.. Can anyone give me a step by step guide that what I need to do?

Not a step-to-step guide but a site on your responsibilities etc:
http://www.direct.gov.uk/en/HomeAndCommunity/Privaterenting/RentingOutYourProperty/index.htm

Get a copy of the rules that apply to you the landlord and read it.Observe all the rules so that your property complies with all the rules regarding safety etc and then you are ready to advertise it.
An advert in your local paper is a good place to start and point out your preferences in it i.e. No smokers,pets,children etc.
Once you get replies,arrange a weekend to arrange viewings of the property by the applicants and those that are interested you can interview and ask for bank and work references and do a credit check on them.Once all these are through,you decide which person you want and organise a lease stating the rules of the agreement between you.You need to have 2 copies,one for them and one for you.Their deposit must be lodged with a deposit holding company for their protection and yours.
If the above seems a daunting prospect,then get a letting agency do it for you and pay them.
A final point,if you have a mortgage on the property you have to inform your mortgagees that you are going to let the property out and they will only give permission if you agree to certain terms and conditions and will probably charge you an extra percentage on top of your mortgage and also insist that you take out a landlord insurance to cover every eventuality.
I think that covers it all.

You might want to consider an online letting agent who can guide you through the process. Regardless of what you decide the following tips might help:
http://www.letpropertyrentproperty.co.uk/latest-news/151-ten-steps-for-new-private-landlords
http://www.letpropertyrentproperty.co.uk/latest-news/145-top-ten-tips-for-private-landlords-letting-property

Ps regarding references you can get these done by experian via online letting agents

Others have given you good advice. The main thing is to select good, honest tenants who will look after your property and pay the rent on time. If you make a mistake, and many do, you will get trouble you never knew existed. Only let to genuine professionals in full time employment who can produce employers, bank, and personal references. It may take longer to find them, but you want long term security not short term problems. Have a good chat to them to get an idea of their personality. If you are at all in doubt move on to the next applicant. I take months sometimes to find decent tenants. You only need one bad one to cost you a fortune in legal fees and sleepless nights. I do not exaggerate.
Also have a look at the link for good basic info on letting.
Advertise in the local and county newspapers.

you need to :

advise your mortgage lender and pay the extra premium
find an agent or be prepared to reference and vet tenants
get suitable insurance
remove all stuff you don't want
clean, redecorate the property
get an inventory done
get gas certificate
get electrical check
get EPC
understand the tax issues
advertise it
get a proper tenancy agreement done

get a book on the subject or go see an agent. Or find the masked landlord's site!