My son is on the Autism spectrum (I self diagnosed him using www.childbrain.com when he was 2, this was later confirmed by a neuropsychologist consultation). For a long time I was in "denial" in that I was still afraid of the label, it took me many months not to cry when I heard the word autism! When we started biomed in Feb of 2004 I finally earned to embrace the label of Autism. 

For most of our kids, there is no one "magic bullet"....rather each therapy or intervention helps our child to heal..... The biomed approach, of diet changes and supplements and detoxification is a very very valuable approach to start with though...because if you can help your child's own body chemistry to be healthy, then you open the child's ability to stay regulated, to be able to stay in an attentive enough state to learn for all of the other great interventions. SI (Sensory integration) can also help the child to stay regulated. These are great great places to start.

There is an important exception to the need for an official diagnosis of Autism (that I have found) and that is if you live in the US and you want your early start or school district to pay for an ABA program. For that case I believe that a full Autism diagnosis can be helpful. For practitioners in the sf bay area that can diagnose, see the sf bay area resources section of this website, under diagnosis.

Here are online screening tools for Autism:
http://www.childbrain.com/pddq6.shtml
http://www.autismeval.com/ari-atec/

Another helpful site: www.firstsigns.org 

In the "Child with Special Needs" Drs Greenspan and Weider explain the term MSDD, Multi System Development Disorder or Regulatory Disorder

MSDD is considered to be on the Autistic Spectrum BUT many, many of the children that get the diagnosis do not KEEP the diagnosis. Translation - with good, comprehensive intervention many of these children have very good outcomes and move right on off the spectrum. If you take a regulatory disorder (the SI sensory processing kiddos) and involve more systems (motor planning, language disorders etc.) then you tend to be moving towards the MSDD piece of the spectrum.

As one parent said "In the end, does it matter if your guy has what some might call "autistic like traits"? What does that tell you? It is only a description not a destination or a "life sentence" and tells you nothing about where you need to go. Don't forget that, even if he does fall in the ASD basket that it is a spectrum diagnosis. IF he IS there who says he'll stay there? Does it really tell you anything?! I don't know how else to say it. Confusing? Sure! But keep focusing on his developmental profile and you will be fine."

Read more on diagnosis from a Floortime/DIR perspective here:

http://www.icdl.com/Newsletter_Vol2_No1.htm

And if you do not have a diagnosis yet, or are newly diagnosed, see this video clip, it is a commercial for autism today, but it also shows what the first months can look and feel like...

www.autismtoday.com/commercial.htm

Another heart warming and tear inspiring video is here:

www.tacanow.com

And get hope from reading this site (I hope), and these sites:

http://www.zerotothree.org/jacob.html Here is a really cool parent story
http://www.curledup.com/boywho.htm The book, the Boy who loved windows is a wonderful account of a family who floortimes
www.hiddenlaughter.com well written blog from another mom in our shoes

www.autismoneradio.org  wonderful archived radio programs
 

And there are many parents on yahoo support groups, waiting to help you!!! See the links page, search on the word yahoo.