Over the next three-plus years he had to collect his evidence as stealthily as possible. Yes, there were the occasional slip-ups, but he was able to get beyond them.
When the headmaster, Dumbledore, returned to him his family heirloom invisibility cloak his first Christmas, he made use of it; but not just in the way Dumbledore thought he would. During that same first Christmas break, during a short period when he'd learned Dumbledore would be away for a couple of days, he made his first moves. He went back to Gringotts for a short visit.
He had to pay them a pretty penny for their help and discretion; but help him and keep quiet about it they did.
He'd also taken a great risk at the end of his second year, when he had to show a little of his true brilliance. He quickly devised a plan to free the house elf, Dobby, from his abusive master, Lucius Malfoy, right in front of the Headmaster. And struck.
That same night, when he was able to sneak out of his dorm and be alone for a few minutes, he called that little elf to him. Less than a minute later, Dobby was secretly bonded to him.
He felt that, while it was a small risk, by having a house elf of his own he could accomplish quite a few things he could not do on his own without too high a risk. The risk was already becoming too high his carefully crafted persona would be seen as the façade it was and having a house elf would alleviate much of that.
Now, three-plus years later since he first re-entered the wizarding world, he finally had his golden opportunity.
He had his letters prepared and, as soon as his name came out of the Goblet as he highly suspected it would, he sent them that same night.
One went to Madam Director Amelia Bones, Director of the Department of Magical Law Enforcement, magical Britain's most senior law enforcement officer. He invited her to the first task as his special guest. Each competitor was allowed one special guest to sit in the judges box with the judges. He chose her.
His letter to her also strongly suggested she bring with her quite a few aurors, the police force of wizarding Britain. He was going to put on a show, he claimed, they'd be talking about for years.
She wrote back stating it would be her pleasure to be his special guest and her honour to attend. However, she also wanted to know what he was planning that would need so many aurors. To her annoyance he refused to tell her.
His second letter went to the Minister suggesting he turn up. His third went to the editor of the Daily Prophet, magical Britain's daily newspaper. And the fourth went to Wizarding Media, the International wizarding world's version of Associated Press. Both were also encouraged to attend.
When Ron Weasley, his supposed best friend, turned his back on him calling him a liar and cheat because his name came out of the Goblet, Harry pretended to be hurt. Inside, he was jumping for joy. It meant one less person watching him too closely. His only major hurdle to finalising setting everything up was Hermione Granger. Though he was annoyed she'd barely left him alone to get things done, he was also quite touched she'd both believed he didn't submit his name and stuck by him. Even when everyone else was calling him a liar and a cheat, she remained steadfast. He was emotionally touched by her active support.
However, even she was not let in on the plan he had devised. He felt her unwavering obedience to authority carried a risk she would tattle on him. And he could not risk that.
And now the day was finally here. He'd met Madam Bones a short while earlier and watched as she rubbed Dumbledore's nose into how she was 'Mister Potter's Special Guest' and, therefore, 'would be sitting in the Judge's box within arm's reach' of the headmaster as the champions went through their first tasks. Aside, Harry asked her to keep a close eye on the old man.
When she'd asked why, he replied, "I'm very sure he's going to try to interfere with what I have planned. You cannot allow him to do that."
Then he said, "And please have one of your on duty aurors keep a very close eye on Alastor Moody. I'll explain during my task."
When she again asked why, he just reiterated, "I'll explain during the task. You're going to be quite shocked."
He'd also met with the editor of the Daily Prophet, Barnabas Cuffe, and given the man a serve about how Rita Skeeter's article on him from the wand weighing ceremony was nothing but fabrications and lies. Skeeter was standing just behind his shoulder when he berated the man.
"Get control of her, Mister Cuffe," he'd ordered the older portly man. "Or the House of Potter will be declaring an honour feud against you and your paper. And, yes, I willbe calling in the full Alliance to join me."
The editor had immediately blanched before he quickly stammered out an apology and promised to ensure Skeeter would not write any more lies about him.
"I will be holding you to that, Mister Cuffe," he firmly stated right back. "Just one foot out of line and my second will immediately be sent to call on you."
"B-But, it would have been Skeeter who wrote―"
"And you who approved what she wrote for publication," Harry cut in. "As such, you are responsible for what slander is published.
It cannot appear in the Daily Prophet without you signing-off on it."
Harry would prefer the woman wouldn't write any stories about him at all, but he was happy enough with what he'd been promised. Knowing Skeeter had stood right behind her editor and had heard every word the man had said, pleased Harry. Cuffe had immediately taken his leave, spun about, grabbed Skeeter by her arm and dragged her off for a 'chat' under a privacy charm.
While you couldn't hear what he'd said to her, both their expressions told the story. Harry hoped Skeeter was now 'heeled'.
The representatives from Wizarding Media had also heard what he'd told the man and promised their articles about him would always be truthful, but maybe a touch fanciful.
"That's fine," he'd nodded back. "Outright lies, though, will see me and mine come after the pair of you with my wand drawn, fire in my eyes and revenge in my heart. Understood?"
They heard and understood.
When he was the fourth to draw his dragon from the Acromantulan silk bag that idiot, Bagman, offered him, he mentally breathed a sigh of relief he was to be the final competitor to face the first task. It meant the three true competitors would not be held up by what he was going to do.
The other three champions all competed in their tasks, averaging between three and five minutes to complete them. And finally he was called into the arena by Bagman using a Sonorus charm.