everything we (richard and i) do is done with visio. it's a decent CAD application. it's pretty intuitive. you won't be disappointed unless you graduate to designing an automatic transmission or the like. turbo CAD is also a very decent application as is autocCAD LT.
start with:
when you open the app there will be 7 tabs [ file - home - insert - design - data - review - view ]
file tab - new button - double click engineering button - select part & assembly - select metric or US units radio button - double click create button
deign tab - size button [ letter, legal, B, C, etc.. ]
design tab - orientation button [ portrait or landscape ]
design tab - page setup < click the little <. thingy and another window will open >
select page size tab - pre-defined size - select ANSI engineering (for Inch pattern drawings) - select drawing size [ A, legal, tabloid, B, C, D, etc.. ]
select drawing scale tab <usually we work in 1:1> - pre defined scale - select Mechanical engineering (Inch units will be in tenths, hundredths, thousandths).
to get started drawing stuff:
home tab - next to pointer tool there is a drop box - select it - chose [ line, ellipse, rectagle, arc, freeform ] after you click and select tool, you drag to open a rectangle, ellipse, or click srart of line move cursor then click to end the line or arc or freeform line.
ping us in a message if you get stuck and pressing the F1 key makes no sense to you. we'll be happy to help you through the problem, assuming we are able to.
youtube is another good help resource.
http://www.youtube.com/results?search_query=visio+&oq=visio+&aq=f&aqi=g4g-s1g2g-s1g2&aql=&gs_sm=3&gs_upl=1384l2412l0l2867l6l6l0l1l1l0l52l231l5l5l0--DL