Graphing - adding axes and point labels

[From Patricia Oakley]

This is not homework, but illustrations of two Mathematica functions to help you visualize relationships in 3-dimensional plots.  You may copy these functions into your own notebooks and use them!

myAxis returns graphic primitives that create an axis in the given component direction with the given label in the given color from lo to hi; the axis is dashed for negative values.  
myPoint includes dashed lines indicating how one might plot the point by hand and a label for the point.

myAxis[label_,color_,component_,lo_,hi_]:=Module[{e,g,o},
o={0,0,0};e=o;e[[component]]=1;
g={color,Text[label,1.05 hi e],Arrowheads[0.02],Arrow[{o,hi e}]};
If[lo<0,g=Join[g,{Dashed,Line[{lo e,o}],Dashing[{}]}]];
g];
myPoint[p_,color_,label_]:={color,Text[label,1.1 p],Dashed,Line[{{p[[1]],0,0},{p[[1]],p[[2]],0},p}],PointSize[Large],Point[p],Dashing[{}]};

Draw a graph of the points and vectors a, b along with part of the plane determined by a and b.

o={0,0,0};p={-2,6,3};q={6,3,-2};Graphics3D[Join[myAxis["x",Orange,1,-2,2],myAxis["y",Darker[Yellow],2,-2,2],myAxis["z",Green,3,-2,2],myPoint[p,Black,"p"],myPoint[q,Black,"q"],{Black,Arrow[{o,p}],Arrow[{o,q}],Red}],Axes->True,ViewPoint->{100,40,30}]

pc:=ContourPlot3D[(x-26/3)^2+(y-2)^2+(z+11/3)^2==392/9,{x,-5,20},{y,-5,20},{z,-20,5},Mesh->None,ContourStyle->Directive[Opacity[0.5],Specularity[White,30]]]

p1:=ParametricPlot3D[{-2t,6t,3t},{t,0,1}]

p2 :=ParametricPlot3D[{6t,3t,-2t},{t,0,1}]

Show[p1,p2,pc,PlotRange->{{-5,20},{-5,20},{-20,5}}]