I working in IT now despite not having any related qualifications on paper at the moment. I'm working towards getting those credentials though. I got in through networking and getting my PMP (project management professional) certification. I'm currently working towards becoming an enterprise architect (certified).
A couple of key things to getting in the door (past HR):
1) HR people are all about risk reduction. HR staff don't get rewarded for hiring good staff, but they do get fired for hiring too many bad ones. From an HR perspective ideally you have 1) credentials (including degrees) 2) a track record of performance 3) come recommended by someone they know (someone in the company will do). Typically anyone having all 3 won't turn out to be a bad hire. They don't hire for intelligence and capability, they are looking to be able to cover their asses in case you turn out to suck. Whatever you do don't lie on your resume, if even the smallest thing is determined to be untrue HR will drop you like a hot potato.
Keeping the above in mind most applicants have some credentials (1), some experience (2) and no internal recommendation (3).
To get credentials spend the money and get some certifications in the area you work in or others related. Pick credentials in areas where you already know the material and have had some experience as well as frequently occurring as a requirement in the type of jobs that interest you, buy the prep books and study and you can be certified inside of a month or two for $300-1000. You can list credentials you are "working towards" as well (helps with the keyword search).
2) Networking (not the computer kind), If you haven't started building a network (of people) start now. Set the objective to add 1-2 people to your network every week (during your job search) once you're employed continue to do this 1-2 people per month. Use a tool like Linked in. Once you get about 30 or more people in your Linked in Network it becomes useful in that you can find someone you can be introduced to that may be able to help.
Key concept in networking: its about informal meetings 10-15 min, at the convenience of the person you want to talk to, to do these things:
1) give something back (listen, or share something that interests them).
2) create the opportunity to meet other people in the area you want to work in
3) learn about the industry you want to work in.
Finding an opening or opportunity and reference from the inside are not the primary objective.
By giving I mean: treat the person with respect like a person, only ask them for what they can give you (aka do not ever ask for a job), ask them for advice, ask them how they got to where they are, and make them feel like you care and are listening (this is the give back).
Think about it from the networking contacts side. Imagine you're the contact: A colleague (Bob) you trust emails you and writes I'd like to introduce you to an interesting guy (you), he's trying to learn about our industry and find out what he need s to know to be able to fit in. A day latter you get a polite email from the guy asking if you'd be willing to share your expertise and advice in a 15 min meeting at a coffee place and time convenient to you or to talk to you by phone for 10-15 min. You agree to meet because 1) you trust Bob, 2) you're curious 3) you have 15 min 4) its convenient 5) it beats working ;).
In the meeting you talk about your own success and answer a few interesting questions and generally feel good about your own success. You leave the meeting feeling like you met an interesting person with good questions (that you could answer). The person emails you a day or two later and asks a follow up question or two and if you have any suggestions of people you know in the industry that would be good to talk to. You liked the guy so you offer to introduce him to Keith and Sharol two of your suppliers. You also agree to join his network on Linked in.
So now how does a network translate into a job? Once you have a network and people know you're looking for work they may let you know, also more importantly when you find a posting in the company they work in you can contact them again and ask them about it, and if they'd be willing to be a reference for HR.
Also they will give you the inside scoop on the industry and answer some of the questions you cant ask HR. It will help you understand what skills you're missing and how to tailor your resume. In the ideal case you can get contact to the hiring manager and have a 10-15 min networking meeting with him/her or even his boss. If the 15mins meeting is positive, they will tell you to apply (remember you don't ever ask for a job) for the position. If they do you can pretty much expect an interview if you don't screw anything up with you resume / HR application.
Typically with networking about only 1 in 5 (or less) contacts lead to a 10-15 min meeting or new contacts. So this is serious leg work. It does however significantly increase your chance of getting an interview and overcomes the credential / HR hurdle. Also once you've built your network, maintain it (send the odd email) then your next job search is way easier since you already have a network.
3) understand that your resume typically gets about 20-30 seconds of review by a human, if that. In some cases computer systems sort and rank candidates based on an online application form. Make sure your resume is tailored to the job description, as is your cover letter, and that you are a reasonable fit for the role, otherwise don't waste your time applying. If the person knows about you already you will get way more time and already be put in the interview pile.
The other thing is to look for postings on company websites or through your network, by the time a job gets posted in the papers or in job sites like monster it either sucks in some way, or has too much competition. 80% of jobs are filled through word of mouth and networking.
To get relevant experience volunteer if you need to (aka open source projects, charities).
my 2 cents.