Material components are an aspect of old school spell casting that is often entirely ignored or employed to severely limit the playability of Magi-c-Users. As DM it's an annoyance to keep track of components used by NPCs so DMs often let this aspect of play slip into obscurity. It's a pity really, spell components add a lot of flavor to the game and provide goals to spell casters and their allies.
One way to remedy this situation would be to allow a vast number of spells to be cast without material components (perhaps to lesser effect) and have special spell effects for when spells are cast with select material components.
Here are three classic spells rewritten (as example) to reflect a campaign where material components are not always required but do boost minimal impact of the spell and have enhanced effects thanks to use of special material components.
Level:1, Duration:instant, Range: 120'
The caster sends forth a dart of magical energy that will inflict 1d4+1 points of damage on a target if a successful ranged attack is made at +4 to hit.
Material Component #1: Arrow, if the caster employs an arrow as a wand when casting this spell any target fired upon will be treated as AC 9 (still +4 to hit) and damage will be 1d6+1. On a damage roll of 1 or 6 the arrow used as a magical component is consumed.
Material Component #2: Silver headed Arrow, if the caster employs an arrow with a silver arrow-head as a wand when casting this spell any target fired upon will be automatically struck for 1d6+1 damage. On a damage roll of 1 or 6 the arrow used as a magical component is consumed. For every 5 levels the caster has an additional arrow may be fired. (note: if any of the missiles come up a 1 or 6 for damage roll the silver-headed arrow is consumed)
Material Component #3: Magical Arrow, if the caster employs a magical arrow as a wand when casting this spell any target fired upon will be automatically struck for 1d6+1 damage with an additional bonus equal to that of the the arrow (so a +2 magical arrow used to cast a magic missile spell will do 1d6+3 points of damage). On a damage roll of 1 or 6 the arrow used as a magical component is consumed. For every 4 levels the caster has an additional missile may be fired. (note: if any of the missiles come up a 1 or 6 for damage roll the magical arrow is consumed)
When using a magical arrow as a wand the caster also adds 10' per experience level to the range of the spell.
Should the magical arrow have any properties beyond a normal bonus those properties are not applied to a magic missile.
Level 1, Duration: 3d6 turns, Range: 240', Area: 20' radius.
A sleep spell causes a magical slumber to be inflicted upon 2d8 HD worth of creatures within the area of effect of 4 hitdice or less that fail a saving throw.
Material Component #1: Alcoholic Beverage, If the caster quickly imbibes an alcoholic beverage while casting a sleep spell no save is allowed. Multiple beverages may of course inflict drunkenness upon the caster.
Material Component #2: Pixie Dust, If the caster hurls forth 2 drams of pixie dust into the air while casting a sleep spell it may either put to sleep (with no save) 2d6+12 creatures of 4 HD or less within the area of effect or allow a single target with greater then 4 Hitdice to be targeted by this spell, a target of 5-8 HD/levels saves at +2, those of 9HD/level save at +4. Duration all inflicted by this spell is until the target is intentionally shaken awake (1-3 rounds per target) or until they hear a rooster crow.
Level 3, Duration: Instant, Range: 240'
A fireball is created which streaks towards it target and denotes in a forceful burst of fire inflicting 5d6 damage to all within a 30' radius. If Hit roll as per a grenade-like weapon is required to target an area with a fireball and a fireball will bounce and detonate 30' from it's intended target on a miss. Interposing barriers and creatures in melee may inadvertently cause premature denotation of a fireball. Casters may not intentionally "bounce" a fireball.
Material Component #1: Bat Guano, A caster may employ a handful of dried bat guano when casting a fireball. The guano is consumed and the fireball will inflict 1d6 pts of damage per casters level (to a max of 10 dice). The fireball is targeted as a grenade like missile at +2 to hit and bounces no more then 20' when using Bat Guano as a material component.
Material Component #2: Dragon Dung, A caster may employ a handful of dried red dragon dung when casting a fireball. The guano is consumed and the fireball will inflict 1d6 pts of damage per casters level (no maximum). There is no to hit roll required when casting this spell with Dragon Dung.
Hope the examples served their purpose in demonstrating a possible method of making material components matter in allowing more effective castings of some spells over the base with the use of material components. I did take the notion that most descriptions assume the use of unspecified components, a DM has no requirement to do so when adapting this to his own campaign of course.
A DM should decide how such knowledge of material components will be presented to spell casters. I'd recommend two separate sets of spell descriptions one for the DM and one for players. Players may be savvy to some of the material components or none at all. The DM thus has a new resource to award PCs/players with.