I won't cover what you can find in other guides but there are a few things that must be said.
* This achievement does not stack - you will not unlock the silver medal or the bronze medal achievements by getting gold.
* Although I performed all Bonus Objectives in the last mission at the end of the level it told me I hadn't won a ribbon - but then it went on to unlock this anyway. I do not know if this is a bug but at least let the game save all the way back to the main menu before getting worried.
Even though I played on hard for my first play through the game isn't really that hard, it is just fiddly and time-consuming. There is one notable exception, the Berne mission.
Berne. The final mission of Act IV, with only Rome and Ground Zero left to follow, both of which are considerably easier. After getting stuck myself and reading various strategies I soon realised none of these really applied to the Hard difficulty. The solution is to not go all-out and build as much as possible, after geting whipped by groups of tripods and devestators I suddenly remembered, the last C&C game I played was the first one on the PC. This exhibits the same trait, the AI will simply not let you get ahead. If you build an airfield or a battle rig it will throw the kitchen sink at you and you will not survive.
Considering the radar as the compass points rather than the 'game' compass (that is, when you center on the construction yard you are not actually facing north, you are facing north east. I am doing this by-the-radar) then you should try the following, in the following order:
* Build a crane. Remember you can click on the crane to access an extra build queue.
* Build a barracks and position it near the north tiberium field. Construct 6 missile squads and garrison the two buildings north of this with 3 squads per building. The first attack comes this way and these squads are quite efficient for the first couple of assaults until the buildings are destroyed.
* Build two Anti-Air guns and place them either side of the refinery entrance to the east, but as far east as can possibly get. As per the missile squads, the AA guns will stop your harvesters being destroyed anytime soon.
* Whenever you run low on power build a new generator.
* Build a war factory. Place this to the east of the construction yard, preferably to the south but to wherever the largest congregation of your vehicles are. This will help them survive the onslaught. Do *not* build any rigs at this point, the AI will go bonkers and rip you apart. Start to build mammoth tanks.
* Build the tech center (remember you have two construction queues and a secondary queue). Once this is down start the rail gun upgrade, and then upgrade all of your generators.
* Try and build another war factory and put it to the north of the construction yard so you have a broad coverage of repairable space to the east.
* Build 6-10 engineers and place them near the construction yard.
Ok, that has been quite intense so far, but do not deviate from this build plan and start the space uplink or airfields or battle rigs, the AI will take you down. As it is you will be pushed to survive the onslaught but it isn't as severe, and this way there are very few devestators to take down.
From now on in, build a couple of missile squads perdiodically to protect the north side, build a couple of new AA guns periodically to replace the ones that will get destroyed on the south side, and then, manage all your vehicles individually to make sure that they get repaired within the field of the war factory. At this point you shouldn't have lost any harvesters yet either. You then need to focus your fire power on one target at a time - when you shoot down a scrin tripod capture it with an engineer and bring it back to your base. Keep churning out engineers to build up your tripod army. Set the pursuit guard stance as well, but you may have to manually attack the devestators (air ships) as they are often just out of range. If you do, remember to bring your tanks back to the war factories. By adopting this low-tech solution you will soon notice how little the enemy throws at you, even though it is a similar frequency of attacks. However it is still a tight run affair, you may lose a building or two, (I lost a barracks and a war factory) - just build them straight back, and keep churning out mammoths from your two factories.
After about 30 minutes or so you will have noticed that they only throw a couple of tripods or devestators at a time at you, and once you have captured half a dozen and have 6-10 mammoths (you probably would have lost 4-6 defending the base) you can now build a couple of battle bases and start on the ion cannon/space uplink.
After another 10 minutes you should be in charge, I set off and destroyed the eastern Bonus Objective with a dozen tripods, 15 mammoths and a battle rig, using the rig to repair what was left, before taking out the northern objective and repairing, finally I hit the ion cannon on the primary objective and rolled in the last 6 tanks or so I had left to finish the job.I still kept churning out mammoths back at base, and as tiberium was getting thin had to assign a couple and a battle base out in the deep to protect the harvesters. Not once did I build a air base.
Hope this helps, this is different from the final two missions where you can just go for it.