- use psi-rods (the soldiers, that are the primary psi attack targets are the ones, who have the lowest psi strength)
- use a lot of smoke grenades (1-2 between your soldiers and aliens to break the line of sight). If they are not seeing you, they can't shoot at you. Smoke is useless if you have not enough of it, it's either 100% effective or 100% useless. You can still shot, if one of your scouts sees the aliens. It's a huge advantage.
- use dogs/scout tanks as scouts (i prefer the dogs, because they are 5x cheaper and can bite the alien ass
)
- use rookies with low stats as secondary scouts (cannon fodder).
- don't hurry, let the aliens come to you and spend their TUs (you can stay in the skymarshall for the first turn and use the motion scanner afterwards)
- weapons (example for 12 soldiers): 2 rocket launchers (large rockets), 2 grenade launchers (or auto-cannons), 2 sniper rifles, 1 flamethrower, 5 assault rifles. Magnum is good as secondary weapon.
- use the HE-ammo carefully, because you can destroy the corpses/items that you can sell
- capturing live aliens is very important (commanders, leaders, engineers, navigators, medics). Use stun rods.
- avoid the night fights, if possible (if ufo crash lands, you can wait till morning)
- use electro-flares in the night fights
- use strafe left/right function (ctrl-click). If you trigger the reaction fire, your front armour can save you (front armour is better as left/right armour).
- research alloy ammo and personal armor ASAP
- switch to Skymarshall ASAP
- switch to Raven ASAP
- use avalanche launchers as craft weapons
- manufacture items for profit (motion scanner, then alien laser rifle)
- you will need 100-150 scientists and as much as possible engineers (manufacture for profit). I usually have 150 engineers in the main base and 250 in the secondary bases
- i usually have 3 mind shields per base (only secondary bases)
- use a good base layout (see Ufopedia: Base Layout Strategy)
I would strongly recommend the Let's play from Meridian (Youtube: Let's play OpenXcom FMP HD)