I want to do it some day soon and i dont know how...
Well, we can certainly fix that, can't we?
1)what should i need to build
(i think i am going to need only a serial to usb and a serial that communicates with the chip)
What you need is an ISP, or In-System-Programmer.
You can build that, but it can be a bit of a chicken and egg problem. You could make a programmer with an atmega328, but you'd have to program the atmega before you can use it to program an atmega...
That said, you might already have the required hardware. If you have an Arduino, you can use it. Read more here:
http://arduino.cc/en/Tutorial/ArduinoISPThat's not a very great programmer, but it'll get the job done.
If you don't have an arduino to use, you can pick up a cheap programmer from $2 and up, on eBay and various other such places.
Search for things like usbtinyisp, uspasp, and so on.
Even if you have an arduino to program with, I'd still order a dedicated ISP. They're faster, and they're $2.
Note that you *can* fuzz up a chip, in which case you might need what's called a HV-programmer to fix it.
As long as you first understand what you're doing, and then do it, you'll likely be fine most of the time, except for when you make mistakes.
2)What is the process
In a tiny nutshell, something like:
avrdude -c usbtiny -p attiny2313 -U flash:w:test_leds.hex
You can either flash your program directly, or flash a bootloader.
Adafruit has more info:
http://www.ladyada.net/learn/avr/avrdude.html3)Can the bootloaded Chip be programmed after the process or shall i do anything else?
I'm not entirely sure if you understand the relationship between bootloading and programming.
You can program a chip *before* you bootload it. Actually, bootloading it is just programming it with a bootloader.
One of the good things about having an ISP, is that you can program the chip *directly*, without a bootloader. You can do that in the Arduino-interface I think, or directly from command-line.
If you do want to use a bootloader, you'd need correct frequency etc, for it to work properly. Other than that, you're good to go.
Hope this helps.
tld