How to shoot long exposure without cable release?

I recently bought a nikon d3100… I want to know how i can shoot long exposure images without a cable release… Will camera's self timer will do this stuff… Also i want to buy a telephoto lens… So please guide me abt a good telephoto lens…

Added (1). Actually am confused between sigma and nikkor… Whether to go for nikkor or sigma…

Why not buy the IR remote - it's only about £10.

Otherwise you have to use the self timer & are limited to 30 sec exposures. You can't do longer exposures on 'bulb' setting without a remote release.

You can shoot up to 30s with the range of shutter speeds. After that it's the B(ulb) setting and if you haven't got a cable release you'll need to keep your finger on the shutter for as long as the exposure is, but touching the camera in a long exposure will more than likely make it shake so the pictures will be shaky.

Telephoto. How much do you want to spend? What range do you need? Nikon, and others, make quite a few.

Edit

Sigma lenses aren't always brilliant and the Nikon ones will be better. You get what you pay for. Look through the various lenses you may be interested in on review websites and get the opinion of the experts, e.g. Links

Then you can judge the performance against cost against what you need and what you can afford.
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Depends how long. You can use the self-timer function but on most cameras this only goes up to 30 seconds (read your manual to see how long it is on your particular camera).

Anything longer you would have to hold the shutter down manually but you would most likely shake the camera at some point, resulting in a blurry picture.