I clearly recall my moving from addicted player to DM. The hints I can provide are the following:

• devise a story. Try to be original, but not too smart. In meatgrinding mechanics such as D&D, players tend to hack and chop through the story, thus ruining the delicate political plot you devised. One interesting strategy is to find the "small line" in a rule that makes things unusual. Example: Once I created a sub-campaign focused on poison trading. Players looked for poison with the proper magic but were unable to find anything. The poison was hidden inside weapons' handles who were carved to hold the poison, thus were unbalanced but looking normal at first glance. The point is that the spell to find poison cannot see anything under lead, and the weapons were internally coated with lead. They had their amount of struggle to figure it out.
• The plot should not be excessively detailed. Let the story write by itself, with a clear initial direction, though.
• create NPC and know them well, they do the actions and decisions that move the story. Give them names, backstories, objectives. Anything the players will do will force the NPCs to act accordingly to their objectives and alignment, hence the DM must know them well.
• Prepare a large notebook with the directions given by my other post
• define a simple rule for DC of unexpected challenges the players may invent and you won't find in the standard ruleset. Take CD 15 as a good measure of an average task that requires some skills to be performed. CD 18 is a hard task, CD 20 an almost impossible task. CD 10 for something relatively easy even for an untrained person (e.g. cutting a tree with a saw, regardless of where it falls).
• Let them make the game, let them speak.
• Learn to improvise, when to throw behind the screen (for random issues), when to do a fake throw (you throw behind just to give the impression that the decision is random, but you coerce the decision for plot purposes) and when not to throw behind the screen (for important throws, such as hits). Learn to throw dice randomly even if there's no reason for that. This disorient the players which could start metagaming in response of the DM throwing dice when something is done or some time passes.
• if you want to keep things fun and relieve some pressure on you, give a staff of wonders to the bard.

I clearly recall my moving from addicted player to DM. The hints I can provide are the following:

• devise a story. Try to be original, but not too smart. In meatgrinding mechanics such as D&D, players tend to hack and chop through the story, thus ruining the delicate political plot you devised. One interesting strategy is to find the "small line" in a rule that makes things unusual. Example: Once I created a sub-campaign focused on poison trading. Players looked for poison with the proper magic but were unable to find anything. The poison was hidden inside weapons' handles who were carved to hold the poison, thus were unbalanced but looking normal at first glance. The point is that the spell to find poison cannot see anything under lead, and the weapons were internally coated with lead. They had their amount of struggle to figure it out.
• The plot should not be excessively detailed. Let the story write by itself, with a clear initial direction, though.
• create NPC and know them well, they do the actions and decisions that move the story. Give them names, backstories, objectives. Anything the players will do will force the NPCs to act accordingly to their objectives and alignment, hence the DM must know them well.
• Prepare a large notebook with the directions given by my other post
• define a simple rule for DC of unexpected challenges the players may invent and you won't find in the standard ruleset. Take CD 15 as a good measure of an average task that requires some skills to be performed. CD 18 is a hard task, CD 20 an almost impossible task. CD 10 for something relatively easy even for an untrained person (e.g. cutting a tree with a saw, regardless of where it falls).
• Let them make the game, let them speak.
• Learn to improvise, when to throw behind the screen (for random issues), when to do a fake throw (you throw behind just to give the impression that the decision is random, but you coerce the decision for plot purposes) and when not to throw behind the screen (for important throws, such as hits). Learn to throw dice randomly even if there's no reason for that. This disorient the players which could start metagaming in response of the DM throwing dice when something is done or some time passes.
• if you want to keep things fun and relieve some pressure on you, give a staff of wonders to the bard.