Is it bad practice to say my callsign first in a transmission to ATC? Usually ATC is saying the callsign of the plane he speaks with first and then starts with the actual transmission. Pilots usually say their transmission first and end it with their callsign.

However, I somehow started to say my callsign first before every transmission. For example: 

Intended:


  Me: Cleared for take-off runway 33, OE-CNK


How I do it:


  Me: OE-CNK, cleared for take-off runway 33



Is this bad practice? Will it annoy the air traffic controller because he has to keep in mind my callsign for the whole transmission? Or is this not very relevant?
It depends on the country where you are flying, and also what the message is.

For example in the UK according to CAP 413 Chapter 2, section 2.48:


  2.48 
  
  Ground to Air: Aircraft callsign – message or reply.
  
  Air to Ground:
  
  
  Initiation of new information/request etc. – Aircraft callsign then message;
  Reply – Repeat of pertinent information/readback/acknowledgement then aircraft callsign.
  


In Germany the normal procedure is to start a message with the call sign, a reply may have the call sign at the end.  From the AIP, GEN section 3.4-9:


  6.1 Procedures for Radio Communications
  
  ...
  
  (4) The call sign shall be transmitted at the beginning of a message.
  A direct answer to a message may be terminated by the call sign
  instead.