1. Explanation: Cast a buff of appropriate rank for a lowbie without opening spell book

Tossing a buff on a player that is significantly lower than you is a hassle because it means opening the spell book and looking for the apppropriate rank of the spell. I will use the example below to help explain how you can accomplish this on any class of character that casts buffs. This script seriously takes the the pain out of buffing lowbies. This is a complicated script and as with any script any typo results in a error message. The example below is the priest class "Renew" buff.
How it works:

1. < if not UnitIsFriend("player","target")then TargetUnit("player")> means if your target isn't friendly (ie.. a mob) then it targets you. So even if you target a mob or a member of the opposing forces in the world then you wil have the benefit of casting the buff on yourself.
2. < for i=r,1,-1 do if (t>=l[i]-10) > This means to start at 1.. and count up while checking the target's level to see if the target is within 10 lvls of the level of each rank of your buff.

Essential knowledge for customization to your character:

1. < r=#; > This is used as a placeholder. You must replace the # with whatever is your current highest rank in the particular buff that the script is designed to cast. This is the only thing you will have to change in the entire script. You will not have to swap anything on your action bars either.
2. < l={8,14,20,26,32,38,44,50,56} > This is what the script uses to check against the players ranking and the targets level. This is done to determine the appropriate rank of the spell to be cast on the target. This enables the script to always casts the highest buff (available to the caster) based on target level. These numbers are the level at which a player gains a new rank level for the buff used in this script. In the case of "Renew" it has rank change at levels {8,14,20,26,32,38,44,50,56}. So in total there are 9 ranks of the renew spell.
3. < CastSpellByName("Renew(Rank "..i..")") > Name of the buff in the script must be programmed this way.

/script r=0;l={8,14,20,26,32,38,44,50,56};if not
UnitIsFriend("player","target")then TargetUnit("player");
end;t=UnitLevel("target");for i=r,1,-1 do if (t>=l[i]-10)
then CastSpellByName("Renew(Rank "..i..")");break;end;end

2. Priests: Power Word: Shield

This one is for Power Word: Shield. Do not forget to replace the r=# with the # of your appropriate rank.

/script r=#;l={6,12,18,24,30,36,42,48,54,60};if not
UnitIsFriend("player","target")then TargetUnit("player");end;
t=UnitLevel("target");for i=r,1,-1 do if (t>=l[i]-10)then
CastSpellByName("Power Word: Shield(Rank "..i..")");break;end;end

3. Mage: Arcane Intellect

This one is for the Mage buff "Arcane Intellect". Do not forget to replace the r=# with the # of your appropriate rank.

/script r=0;l={1,14,28,42,56};if not UnitIsFriend("player","target")
then TargetUnit("player");end;t=UnitLevel("target");
for i=r,1,-1 do if (t>=l[i]-10) then CastSpellByName
("Arcane Intellect(Rank "..i..")");break;end;end

4. Druid: "Mark of the Wild"

This one is for the Druid buff "Wark of the Wild". Do not forget to replace the r=# with the # of your appropriate rank.

/script r=0;l={1,10,20,30,40,50,60};if not UnitIsFriend("player","target")then TargetUnit("player");
end;t=UnitLevel("target"); for i=r,1,-1 do if (t>=l[i]-10)
then CastSpellByName("Mark of the Wild(Rank "..i..")");break;end;end