The first tool, the lasso tool, is easy to understand but difficult to use accurately. Just drag around the edge of the area you want to select. When you let go of the mouse button, a line will be drawn back to the starting point to complete the selection.

The second tool, the polygonal lasso tool is so easy to understand and use that I recommend you choose this lasso tool most of the time. See for yourself how this works by choosing it and then clicking a few points on the image. When you want to close the shape either just double-click or click once on the starting point. You might think this would be a bad tool to use to select areas with curved ages but you can follow the curves fairly accurately as long as you are patient and willing to click, click, click frequently as you work your way along the curves.

The last tool, the magnetic lasso tool, is fun to use and sometimes a lot faster than the regular lasso tool but I still prefer the polygon lasso tool for most jobs. The magnetic lasso tool tries to detect the edges along the line that you trace with the mouse and it does a good job if the edge is clear. It will go wrong through if there isn't enough contrast between dark and light to mark the edge of the shape. If you try to select the dolphin below, for example, the magnetic lasso will do a good job along the dolphin's back, where the contrast is high, but a poorer job for the dolphin's head because the water in the background is not so bright.

It's hard to know how to set the tool's options for the best result - I suggest you set the lasso width to 7, the frequency to 50 and the edge contrast to 10% (see the Photoshop help system for more).

Once you have clicked to place the first 'fastening point' then you should trace around the area without holding down the mouse button. However, if the edge is not clear then give the tool some help by clicking with the mouse to place extra fastening points. If fastening points start appearing in the wrong places then press the Delete key to delete them and you can try again. You can temporarily switch to the lasso tool by holding down the Alt key and then dragging the mouse.

Test your selection skills by using the polygon lasso to select Sugar, the dolphin in the photo below, using a feather size of 1. Ignore the hoop. Don't worry if your selection isn't very accurate - you can add to or subtract from the selection after your first rough selection is complete. To add to the selection, switch to the lasso tool, then hold down the Shift key while you select the area to be added (look for the little '+' sign while you hold down the shift key). Complete the selection before you let go of the shift key. To subtract from the selection using the lasso tool, hold down the Alt key while you select the area to be subtracted (look for the '-' sign).

When you are satisfied that the selection is accurate, make a copy of the selection by using Ctrl-Alt-Drag i.e. hold down the Ctrl and Alt keys (the pointer will turn into a double arrow) and then drag the selected area. This is like a short-cut for copying and pasting except that copying and pasting would put the copy in a new layer whereas the Ctrl-Alt-Drag trick puts the copy in the same layer - it does not make a new layer. With the copy still selected, flip it to face the left by choosing Edit>Transform>Flip Horizontal. Then you can make the dolphin into a baby dolphin by choosing Edit>Free Transform and dragging one of the corner handles. If you hold down the shift key while you drag the handle then you will make sure that the dolphin keeps the correct proportions and does not get squashed or stretched, so this is a good idea. When you have adjusted the size of the dolphin to your liking, press Enter to let the computer know you've finished. Drag the baby dolphin to wherever you want it to be. If you're bothered by the piece of hoop that you can still see crossing the baby dolphin's body then do something about it! (Rubber stamp tool?)

Now that Sugar has some company you can save your picture as a jpeg. As usual, if you are using Photoshop version 5 then you won't be able to save in the jpeg format until you first flatten the two layers in your picture into a single layer with Layer>Flatten Image (Calque>Aplatir l'image) -  this step is not necessary in version 6.