When it comes to applying for jobs, it is often a numbers game, the more you apply for the more chance you have of getting invited to an interview.
If you are not really bothered about what you do, you just need a job quickly then you can apply for a range of positions but remember to tweak your cover letter and possibly CV each time you send it out to highlight the points that are relevant to the position you are applying for.
If you have a job in mind that you would like to go for then search the internet and local papers to find positions that suit what you are looking for.
If the job advert asks for skills or experience that you do not have then you may still wish to apply. Remember if you do decide to do this then you may need to explain why you feel you are suitable for the position even though you do not have everything they have asked for. It is always worth mentioning that you are happy to undergo training to get to the level that they want you to be at and possibly to consider a pay drop should they offer you the position.