1 - Start with a cylinder

Using the photo above, I drew an outline of the core body shape and sketched out where the joints of the legs would be. I used this outline as a backdrop to my left viewport for reference. This image sets the base scale of the model.

The next stage was to create a cylider for the base shape of the body. Rotate it and scale it to cover the outline image. Here, I am only using half a cylinder as we will mirror the other half later on. This makes it simple to arrange the base vertices without having to worry about the other side. Keep the number of segments to a minimum, just to allow you to sketch out the rough shape, you can always add vertices and edges later.

Max shortcut - use Alt-B when the left viewport is highlighted and browse to your reference image. Be sure to check the Lock Zoom/Pan option and Match Bitmap.

2 - Fit to shape in side view

Now add an Edit Mesh or Edit Poly modifier so we can pull the vertices around. Just concentrate on the side view and pull the vertices to roughly match the outline. You can be fairly rough to start with and tweak later. Try to keep the cross-sections in line so they follow the contours of the body. Also, bear in mind where the joint sockets are and try not to create a line over them at this stage.

One good technique is to move the whole mesh down below the sketch first. This way, you can pull vertices from the top edge without the rest of the edges distracting your view. Once the top is done, do the next and then the next until you can fill the bottom edge. Also, think in percentages, the top line goes at the top, the next is 25% away, the next should be 50% between top and bottom etc.

I would also recommend using a graphics tablet if you have one as it is very natural and quick to grab the vertices and drag them into position.

3 - Fit in all views and refine

The next step is to cover the other dimensions and slide the vertices in the perspective view along the one axis that wasn't covered by the side view, in this case it was the X axis. Slide the interior vertices only, keep the border vertices flat along the axis plane as we will mirror the model later.

Roughly drag them into place, working along the body and then go back and refine if necessary. There is no need to be super particular at this stage, we are only sketching out the basic shape of the model.

You may notice that I have also added another cross section near the hip to give me more detail. You can use the Edge Loop/Ring Connect tools in the Edit Poly Modifier. This works by selecting an edge linking two cross sections, then select the ring of edges, then use the connect tool to split the ring down the middle. The default is one division, but you can add more in one go if necessary.

4 - Fix line density in tail

Now if you look at the tail section, you will see that the polygons there are long and thin. There are too many edges running along its length and not enough cross section.

We really want to cut down the number of long edges. The solution here is to collapse some of the edges which are too short..

There are two ways you can do this, by collapsing edges or welding vertices. If you want the result to be the average of the two edge lines, use collapse. If you want an edge line to simply disappear, use target weld. Here, I used target weld.

5 - Add sockets for arms and legs

Now we need to establish where the sockets will be for all the limbs. Those 3 triangular polygons we created in the last section will make a good socket for the rear legs and it will allow us to draw the 3 sided polygons to the tip of the limb and thus keep our topology clean and quadrangular.

The other two are simple 4 sided polys. Feel free to add more cross-sections to help define the socket placement. Once the socket polys have been selected, we simply extrude or bevel the faces out a little to create the start of our limbs.

Don't worry if the placement is not exact, at this stage we are still working with as few polys as possible to make it easy for us to quickly push the shape around vertex by vertex. Try to stay in "sketch mode" in your head and don't get too precious with your polys.

6 - Add more detail

Now we can continue sketching out the shape of the body, adding more detail where necessary and keeping the topology as clean as possible. Work in all views, push the vertices around to get the shape you want. Look at the limb sockets and make sure you allow enough space for the body to blend into the limb.

I have added more edge lines to the sockets to make each cap hexagonal. By setting each limb to 6 sides, I can use just two four-sided polys to cap the end of the limb. This is great as it keeps the topology clean and the edge loops complete. This is not essential, but it can really help make it easy to add detail along edge loops later.

7 - Refine head & mirror

Notice that in the last step I pulled back the vertices around the head. Now we can go back and work our way up the head. Select the border edges around the neck and then shift-move them to create another row of faces. Then pull the new vertices into position. You can then add more rows util you get to the end where it is a simple matter of creating a new face to cap the tip.

At this stage I have also made a mirror copy of the mesh to get a better understanding of what the whole body will look like. Use select mode and world axis and pivot before you mirrror to make sure you pivot about the centre of the grid. When you mirror, make an instance of the mesh, so that any future changes are reflected on the other side.

Now that you see the whole body, you may want to refine the vertex positions and create the overall shape you want. Make sure the border vertices lie on the centre axis to make the two halves seemless. Add some more detail when you are happy with the overall shape. Don't worry too much about the limb sockets or head area as we will get to them later.

8 - Close head & refine shoulders

Working around the head and shoulder area, we can close the mesh by adding faces at the end. You can use the cap holes modifier or create a new face directly. Notice that at this stage we are still maintaining 4 sided polygons wherever possible.

Start working the vertices around the shoulder out to create the sockets for the arms. Change the smoothing group at the ends to give you a better idea about the shape and which areas are to be extruded.

Also, fill out the chest cavity to make room for the pectoral muscles.

9 - Start arms & chest

Now we can start extruding out the arms. Shift move the end faces to create more arm cross sections. Just work on the first few for now. What we are trying to achieve here is to line up key vertices along muscle lines. The most obvious is the line that runs underneath the pectoral muscles and swoops up into the arm. Have a look at anatomy reference books and you will see what I mean.

It is important to try to follow these key muscle lines as they not only define the shape of the model, but also how the vertices move when animated. These lines are usually most visible where large muscle groups intersect under the skin or where hard sections of bone are indicated.

10 - Create base arm

Select the base arm faces and detach them from the main body. This will allow us to work on the arm in isolation without having to worry about the rest of the mesh.

Extrude out some more faces to define the arm and start shifting vertices around. You could use reference pictures of your own arm here in the top and front viewports to help get the dimensions correct. Alternatively, see if you can find some pictures on the net.

Push the vertices around to create the contours of the arm. Note where the elbow crease will be and the key bulges of the triceps, biceps and forearm muscles.

11 - Refine arms onto body

With the basic arm sketched out, we can re-attach it to the shoulder. Now we can see what the arm looks like on both sides.

Assign the faces back to one smoothing group and start shifting vertices around to get the arm shape you want. Make sure you blend the arms well into the shoulder to prevent them from looking like sticks shoved into the shoulder.

I cannot stress enough how much anatomy reference helps here. Gather all the books you can afford, look on the net and study your own body. Note where muscles start and end, where the major groups are and how they attach to the bones. Muscles constantly overlap each other like the deltoids covering the instertion point of the pecs, try to follow the contour lines and match them with your vertex placement.