Sheedee: here is what I do. Both methods employ Wardrobe Wizard.

 

1: Morph you character as you wish.

2: Using WardrobeWizard create a MOR file of the figure (from WW menu/"Utilities"/"Morphs"/"Create MOR From Figure", name it something you like - I use a reusable name like "temp").

3: Using WardrobeWizard do a conversion of the clothing item by using WW's "Convert". Select your clothing item's CR2 file, use the figure as both the source and target of the conversion (unless of course the item is originally made for some other figure), tick the "Add Full Body Morphs" selection among other selections you may want. When the conversion begins, select your "temp" MOR file you created in in step 2 - it's now available as a FBM of the figure in a list of that figure's morphs. Let WW do it's magic in peace.

4: Load the clothing item from library. WW creates a root folder for your model in Runtime/Libraries/Character. Conform. In "Body" actor of the clothing, you now have a dial for the created FBM "temp". Dial it to 1.0. In most cases you now have fitting clothing. Sometimes you may want to go slightly above 1.0 or perhaps use some of the other provided additional morphs like "inflate/deflate", "shrink/wrap".

 

The drawback to the process being the (sometimes obscene) amount of time spent on analyzing a particular clothing item for the first time. 

 

---

The following method is faster, but uses D3D's "Morphing Clothes" (http://www.renderosity.com/mod/bcs/morphing-clothes/64629), which is not free but then again not that expensive for what it does for you.

1: Morph your figure as you wish.

2: As in the previous method, use WW, but select the "Dials to Single Morph", name your morph something (like "temp"), then save your figure as a new figure. 

3: In "Morphing Clothes", you would now load both the figure saved and a clothing item made for that figure.

4: Transfer the "temp" morph to the clothing item and save the clothing item. Back in Poser, the saved clothing item now has a morph named "temp", which when conformed to original figure will fit when dialed to 1.0.

 

Method 2 is faster because WW doesn't need  to analyze the clothing items, but not usable when you want to use clothing items that are originally made for another figure. Personally I NEVER save the files over the original items, but create temporary files that I annihilate after I have completed the scene I'm working on.