Draw sugars from memory, then convert, flip and link them.
The carbon chain runs top to bottom with C-1 at the top. Horizontal bonds point toward you. A D sugar has the OH on its highest-numbered stereocentre on the right; an L sugar has it on the left.
Groups on the right in the Fischer projection point down in the ring; groups on the left point up. On the last ring carbon of a D sugar the rest of the chain (CH2OH in a hexose) points up. In an L sugar it points down.
For a D sugar, α has the anomeric OH down (opposite the CH2OH) and β has it up (same side as the CH2OH). For an L sugar it is the other way round.
Up stays up and down stays down. Each ring carbon has one axial bond (straight up or straight down) and one equatorial bond (out to the side). Axial bonds alternate up, down, up, down around the ring.
A pyranose is a six-membered ring (five carbons and one oxygen). A furanose is a five-membered ring. Only six-membered rings have a chair.
A five-membered ring puckers into an envelope: four ring atoms lie in one plane and the fifth sits above or below it. The atom is endo when it is on the same side as the carbon that hangs off the last ring carbon (C-5 of ribose), and exo when it is on the other side. The envelope is drawn from the side, almost edge-on, with the thick edge nearest you and the ring oxygen at the back. Up and down for every group are the same as in the Haworth drawing.
Click a carbon in any drawing to flip it. Point at a carbon to find it in the other two.
The anomeric carbon of sugar 1 bonds to an OH of sugar 2.
Or build your own: choose any two sugars and the carbon that takes the bond.
Two sugars that differ at exactly one stereocentre. D-Galactose is the C-4 epimer of D-glucose; D-mannose is the C-2 epimer.
Two ring forms of the same sugar that differ only at the anomeric carbon (C-1 of an aldose, C-2 of a ketose). That carbon is not a stereocentre in the open chain; it becomes one when the ring closes. In water the two anomers interconvert through the open chain. This is mutarotation.
Enantiomers are mirror images: every stereocentre is flipped, which is what D and L forms of one sugar are. Stereoisomers that are not mirror images are diastereomers. Epimers and anomers are both kinds of diastereomer.
Name the sugar that gives its anomeric carbon first, ending in -osyl, with its anomer. Give the two carbons in brackets, such as (1→4). Then name the second sugar. If both anomeric carbons are in the bond, use a double arrow, such as (1↔2), and end the name in -oside.
A sugar with a free anomeric carbon can open to its aldehyde or ketone form and reduce Cu2+, so it is a reducing sugar. If both anomeric carbons are locked in the glycosidic bond, as in sucrose and trehalose, neither ring can open and the sugar is non-reducing.
Structures follow the usual textbook conventions. A side chain of two or more carbons outside a Haworth ring is drawn as a Fischer fragment. Equilibrium percentages are approximate values for water near room temperature.