user7203: I wish to use a MOSFET to drive a 12V rated LED strip from an Arduino.
The negative side of the LED strip must be connected to ground, so that means that the driving MOSFET must be between +12V and the LED strip. 
This is what I have tried so far. 

The load must be between my mosfet and my car battery GND.

user6959: In your existing arrangement.
Swap to P Channel FET
Swap drain and source leads (right hand two).
This will work for up to 5V feed to LEDs.
To get 12v operation you will need to add a driver between the FET gate and the Arduino.
see circuit diagram below.

To operate with FET on the HIGH (V+) side when V+ is greater than the rduino's supply voltage, the FET must either

Be P Channel with FET source to +12V and FET drain to load+ or

An N Channel with gate drive above V+.
The gate drive to the FET must go to about +12V to turn it off.
The Arduino will only drive it to +5V.


As you are unlikely to want to provide an extra high side drive the P channel option is preferred. This could be eg:

A "jellybean" bipolar transistor or small FET worth a few cents) and a few resistors, or a small N Channel MOSFET and one resistor

or

An opto isolator.


Transistor driver:
Bipolar transistor NPN (BC337 / BC817 or similar)(ANYTHING NPN will work).
R1 = 10k resistor Arduino out to base.
R2 = 10k FET gate to +12.
If an N Channel MOSFET is used for Q1 then R1 is not needed.
This could be a  5LN01SP IF you can get them - no stock Digikey.These have a very low Vgsth (turn on voltage)
Otherwise you can use a 2n2222, VN2222, BS108 or similar logic-gate N channel MOSFET.
eg VN2222. Many variants of these are widely available and low cost.

simulate this circuit – Schematic created using CircuitLab

7203: <p>I wish to use a MOSFET to drive a 12V rated LED strip from an Arduino.<br>
The negative side of the LED strip must be connected to ground, so that means that the driving MOSFET must be between +12V and the LED strip. </p>

<p>This is what I have tried so far. </p>

<p><img src="https://i.stack.imgur.com/T4jlD.png" alt="led strip mosfet arduino"></p>

<p>The <strong><em>load must be between</em></strong> my <strong><em>mosfet</em></strong> and my car battery <strong><em>GND</em></strong>.</p>
 6959: <p>In your existing arrangement.</p>
<p>Swap to P Channel FET<br />
Swap drain and source leads (right hand two).</p>
<p>This will work for up to 5V feed to LEDs.</p>
<p>To get 12v operation you will need to add a driver between the FET gate and the Arduino.<br />
see circuit diagram below.</p>
<hr />
<p>To operate with FET on the HIGH (V+) side when V+ is greater than the rduino's supply voltage, the FET must either</p>
<ul>
<li><p>Be P Channel with FET source to +12V and FET drain to load+ or</p>
</li>
<li><p>An N Channel with gate drive above V+.</p>
<p>The gate drive to the FET must go to about +12V to turn it off.<br />
The Arduino will only drive it to +5V.</p>
</li>
</ul>
<p>As you are unlikely to want to provide an extra high side drive the P channel option is preferred. This could be eg:</p>
<ul>
<li>A &quot;jellybean&quot; bipolar transistor or small FET worth a few cents) and a few resistors, or a small N Channel MOSFET and one resistor</li>
</ul>
<p>or</p>
<ul>
<li>An opto isolator.</li>
</ul>
<hr />
<p><strong>Transistor driver:</strong></p>
<p>Bipolar transistor NPN (BC337 / BC817 or similar)(ANYTHING NPN will work).<br />
R1 = 10k resistor Arduino out to base.<br />
R2 = 10k FET gate to +12.</p>
<p>If an N Channel MOSFET is used for Q1 then R1 is not needed.</p>
<p>This could be a  <a href="http://www.onsemi.com/pub_link/Collateral/EN6559-D.PDF" rel="nofollow noreferrer">5LN01SP</a> IF you can get them - no stock Digikey.These have a very low Vgsth (turn on voltage)</p>
<p>Otherwise you can use a 2n2222, VN2222, BS108 or similar logic-gate N channel MOSFET.<br />
eg <a href="http://www.onsemi.com/pub_link/Collateral/VN2222LL-D.PDF" rel="nofollow noreferrer">VN2222</a>. Many variants of these are widely available and low cost.</p>

<p><img src="https://i.stack.imgur.com/OQdAa.png" alt="schematic" /></p>

<p><sup><a href="/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2fOQdAa.png">simulate this circuit</a> &ndash; Schematic created using <a href="https://www.circuitlab.com/" rel="nofollow">CircuitLab</a></sup></p>
