For Xbox players...
Notes for par scores on all levels:
Par scores are heavily influenced by par time.
Note: Competitive Score shows the time multiplier bonus; Regular Score does not. The time multiplier bonus still exists in Regular Score, it only shows up at the end of the mission. With Regular Score, you may not see the time bonus, especially on longer missions (credit: EaseAndInspire)
During "par time" all scoring is tripled.
After "par time", you have 10 minutes where your multiplier goes from 3.00x down to 1.00x. For example, if you kill an elite for a pop up of "+200", the score will show 600 during par time, but then will trickle back down to 200 when the multiplier goes down to 1.00x (and will be 400 if the multiplier is at 2.00x).
After the "ten minute down to 1.00x" period, one of two things happen:
1. You get a 2nd grace period, of about 10 more minutes. Multiplier is already at 1.00x so nothing else happens with it.
2. All positive scoring is done. All kills show up as red "0", but you will still lose points for dying, team kills, or checkpoint resets.
After that (Par time + 10-minutes + possible grace period), all positive scoring is done no matter what. Negative scoring is still active.
If you've already achieved the par score, you'll still have to beat the level while making sure you don't have enough negative scoring (deaths) to go below it.
Most missions I went with the following:
Difficulty: Heroic, due to the added multiplier
Skulls: Catch (extra grenades all throughout - although you will get stuck from time to time), Famine (there's still plenty of ammo), Fog (no radar - but enemies are easy to spot without), Thunderstorm (all silver elites DO NOT upgrade to gold so this skull isn't as bad as it would seem), Tilt (Per TheOdd101, plasma weapons are more effective vs shields and most UNSC weapons are less effective vs shields), and Cowbell (non-scoring but accelerates explosions)