How can I get my redstone to activate adjacent pistons?

I'm trying to create my first circuit in minecraft:

• a - pressure plate
• p - piston
• d - dirt
• - or | - redstone

a----dddd
     pppp

Pistons are placed over the dirt and there's water under the dirt.

I'm trying this but it doesn't work:

a-------
     ddd
     ppp

This also doesn't work:

----
a ||
  dd
  pp

This does work, but only if pistons aren't adjacent

a--------
    | | |
    d d d
    p p p

Here are two screenshots:

This doesn't work

This works:

Solution 1:

There are actually a large number of different ways you can do this. Perhaps the simplest is using redstone repeaters, like so:

There's also the design proposed by StrixVaria, which uses elevated redstone:

But there are even more ways you can do this. Here are a few:

Take your pick!

Solution 2:

Try this:

a---+++
    ppp

• a - pressure plate
• - - redstone
• + - redstone on a raised block (the block should be at the same level as the piston)
• p - piston

Solution 3:

In order to power pistons, you either need the redstone line running directly into the piston, run the redstone line on a raised block, or using redstone repeaters. You can also power an adjacent block using a repeater, which can be very useful for certain applications.