Hits, Tips, & Strategys: Pokemon Sapphire - Guide for Pokemon Sapphire

Before I start, I'll tell you that this is NOT a walkthrough. It is used to HELP you 
get through the game. (* means that I copied them from the Pokemon Ruby & Sapphire 
Guide [PrimaGames], ** means that I copied from the Pokemon Ruby & Sapphire Guide  
[Nintendo Power])

(1)Pickup Crew:

Capture 6 Pokemon with the Pickup ability (Zigzagoon, Linoone, & Phanpy), fight weak 
pokemon for awhile, & check your pokemon (make sure that they aren't holding 
something you gave them). You can get Protein, Full Restore, even a King's Rock in 
very rare occasions, plus others. But the most useful item is the rarely found PP 
Up. Get a few of them, & use them to increase the PP of the moves of the pokemon you 
use most often that have the lowest PP. You can only use them 3 times per move, but 
it increases the PP of that move by 1/5 of its original PP value (5 PP moves get 1 
more PP each time, maxing out at 8; 20 PP moves get 4 more PP each time, maxing out 
at 32). This is especially useful for Battle Tower & Pokemon Collesseum. The full 
list of Pickup items & rarity of them are as follows:

*Often Found: Super Potion
*Sometimes Found: Ultra Ball, Full Restore, Full Heal, Nugget, Revive, Rare Candy
*Rarely Found: Protein, PP Up
*Very Rarely Found: King's Rock

(2)Unbelievable Rayquaza Capture:

This is how I managed to capture Rayquaza with little effort without a Master Ball:

Turn 1:

Lv.70 Rayquaza appears
Sent out Lv.49 Grovyle nicknamed "Secptile"
Chose attack Leaf Blade
Rayquaza used Outrage for 122 damage, knocking out Grovyle
Sent out Lv.49 Kyogre Nicknamed "Kyogre"

Turn 2:

Chose attack Blizzard
Rayquaza used Outrage for 100 damage
Kyogre used Blizzard to get Rayquaza's health down to a sliver of red
Rayquaza became confused out of Outrage's side effect

Turn 3:

Used Ultra Ball to successfully capture Rayquaza
Nicknamed Rayquaza "Rayquaza", which is sent to Box 5 in PC

I got REALLY, REALLY lucky. It most likely won't work even if its frozen with 1 HP.

(3)Boosting Jirachi's Stats Massively

There are some natures that make pokemon like all pokeblock flavors equally, have 
their stats boost equally, &, if its a Shadow Pokemon (found only in Pokemon 
Collesseum), the 5 ways to lower its Taint Meter have equal effect. *These natures 
are Bashful, Docile, Hardy, Quirky, & Serious. If you recived a Lv.5 Jirachi through 
the Pokemon Collesseum Bonus Disc that has one of these 5 natures, then don't level 
it up yet! When you get the Macho Brace from the Winstrate family, give it to 
Jirachi. When equipped, the Macho Brace ups the growth of stats while halving the 
Speed during battle. This will give it a major boost in stats, yet I don't know why 
Jirachi won't recive benefits from vitamins.

(4) Use A Well-Rounded Team

Have a team of a varity of types. Don't have an all-Ground team or a Rock, Ice, & 
Steel team. Use pokemon that have strengths of the weakness(es) of another pokemon. 
Example:

Gardevoir, Psychic

Mightyena, Dark

Ninetales, Fire

Kyogre, Water

Regirock, Rock

Muk, Poison

It's also good to teach moves to them that are strong against the pokemon it's weak 
against. Example:

Gardevoir: Thief, Hypnosis, Dream Eater, Psychic

Mightyena: Shadow Ball, Crunch, Scary Face, Aerial Ace

Ninetales: Fire Blast, Iron Tail, Sunny Day, Roar

Kyogre: Blizzard, Earthquake, Water Spout, Sheer Cold

Regirock: Superpower, Zap Cannon, Lock-On, Curse

Muk: Giga Drain, Minimise, Sludge Bomb, Disable