Merry Christmas, Photoshoppers.  Here's a little gift for you.  :-)

I confess.  I don't even try to use the standard Lasso.  It's beyond my limited skills.

The Magnetic Lasso is a different story.  The Magnetic Lasso senses the edge of the object you are outlining, and snaps itself to that edge.

To try it out, first open the image file containing the object you want to select.

Click on the Magnetic Lasso Tool.  If you only see the standard Lasso, click on the tiny arrow in the lower left corner by the Lasso icon.  That will bring up the Lasso sub-menu.

Click on a starting point in your image, at an edge of the object you want to select.  Slowly and gently guide the cursor along the edge of the object.  Resist the temptation to click every couple millimeters.  As long as there is some contrast between the object and the background, the Magnetic Lasso will find the edge, and it will set "points" along the way as you guide it.

I find I like to hold the cursor just a teensy weensy tiny bit above the outline of the image, and let it fall to the edge. 

Note that you do not need to hold the mouse button down as you guide the cursor along the edge.

Note that you can adjust the settings for the Magnetic Lasso. 

Width tells the magnetic lasso just how far away in pixels to search for the edge. 

Edge Contrast tells the lasso just how sharp a contrast to use in finding the edge.  Use a low number for soft, low contrast images.  Use a higher number for higher contrast images.

Frequency tells the Magnetic Lasso how often to mark a point.

Just keep gently guiding the cursor along the edge of the object.  Think easy, relaxed, don't even hold the mouse button down; just let the Magnetic Lasso find the edge on its own.

If you come to a really tricky edge - like the fish's fins, you can go ahead and click to manually mark the point, but for the most part, clicking isn't necessary. 

If you make an error, stop and click the Backspace key.  Clicking Backspace will remove the most recent marked point, but note that it does not move the cursor backwards.  Gently guide the cursor back towards the edge, at this point you may want to click to manually set a point, then continue moving along the object's edge.

Your selection isn't finished until you come all the way back to your starting point.  When you get back to the starting point, click on that first point to close the selection.

After closing the selection, you might notice an area that needs a slight adjustment.  Here's a little trick to make adjustments:

With the object still selected with the border of marching ants, click on the Selection Brush Tool:

Be sure to choose the Selection Brush Tool, not the Magic Selection Brush Tool.  Why?  Because the Selection Brush Tool is the gateway to Masking mode. 

After you click on the Selection Brush Tool, look up at the Options bar.   Click the drop-arrow menu arrow at Mode, and choose Mask. 

Choosing Mask will place a red overlay over everything in the image except the object you selected.  (Trivia note:  The red overlay in Photoshop was designed to resemble the red acetate "rubylith" used by print shops when masking images the old school way.)

To add to the red overlay area, just click and drag the cursor over the area.  Note:  adding to the overlay subtracts the area from the selection.

To subtract from the red overlay, hold down the ALT key, then click and drag the cursor over the area.  Note:  subtracting from the overlay adds the area to the selection.

Does that sound odd?  Don't worry.  Just try it a few times, and it will soon make sense.

Note that you can adjust the brush size as you add and subtract to your selection

Once you have tweaked the selection to your satisfaction, back in the Options menu, click the drop down menu at Mode: and choose Selection to remove the red overlay.

The red overlay will disappear, but your edits to the selection outline will remain.  There, now you have a completed selection ready to stylize, or drag onto a new background.

Many Thanks to Barbara-Jo and Bill of Exit Realty in Florida, for the fish mailbox image!!!