How to get a Togepi
Togepi is one of the first pokemon you can get in gold/silver. Near the very beginning you will be given
an egg by the professor. You will have to give it away for a short time, but it's given back to be put in
your care. If you walk around with this egg in your inventory, after a long time it will hatch into a togepi.
How to get any pokemon from red/blue/yellow
One feature of gold/silver is the 'time machine'; the time machine is found on the second floor of all pokemon centers.
Using this feature, you can trade pokemon with older versions of the game so long as you have no pokemon or attacks in
your party exclusive to gold/silver. You can use the GameShark codes to catch any pokemon (found on the main page)
and then trade it over to gold/silver. By employing this method you can add mew, mewtwo, articuno, zapdos, moltres, etc. to your party.
Unfortunately, many of the very rare pokemon can not be bred in gold/silver.
How to get expensive/important items early in the game
A new addition to the game is you're now able to 'equip' your pokemon with an item. You can take advantage of this
in order to receive an item from a more advanced stage in the game. If you have a friend who is further in the game,
he/she can buy an item, equip it to a pokemon, and trade it to you. Now you can un equip the item and have it in
your possession. You can use this to get potions, rare items, or any other expensive or unavailable item.
How to make your pokemon very strong early in the game
This trick requires a friend with an advanced game. Trade your pokemon to the friend, and have him teach any hm/tm that you desire. Because in gold/silver you are given the option of removing HMs (by a man found in the dragon town) there is no reason not to teach the pokemon any good HM you can find, so long as there's a free slot. You can also buy thunderpunch, icepunch, and firepunch at the large pokemon mart in the western world. The Cerulean City Pokemon Mart is still open in the eastern world, so you can also have an advanced friend buy from there. A winning strategy would be to select the crocodile pokemon at the start, trade to a friend, and have him/her teach it icepunch and surf. Now you have icepunch (very strong against bird trainers) and surf (a great all-around water attack). These attacks will give you a HUGE advantage early in the game.
How to make a super-team by the time you reach the 2nd city
Another friend-helping trick. Early in the game, catch many useless pokemon to trade. While you're doing this, have your friend breed all the Pokemon that you want for your team. Make sure your friend deposits all the eggs he/she receives in the PC until they're ready to be traded. Now trade all your useless pokemon for these eggs. Now walk around with these eggs in your party, and after a while they'll each hatch into a level 5 pokemon of the type you bred for. The pokemon will be yours, meaning that you'll be counted as the original trainer. Meanwhile you'll need a good pokemon for fighting with (egg-hatching takes time) so I'd recommend using the previous trick first.