Saudi Arabia should send its GID intelligence service officers to train in Israel and Jordan. Because even aside from its immorality and unjustifiable risks, the Saudi intelligence operation to kidnap or kill Jamal Khashoggi was an unmitigated debacle.
The GID failed to cover its tracks, and by its action it has drawn massive global pressure onto its government. Indeed, the Khashoggi operation exemplifies what is known in intelligence circles as "blowback": an action that causes far more negative outcomes than sought. While it's not yet clear how the Saudis will play out this situation, they must ensure they don't screw up like this again in the future.
The best way to do so is for them to seek the expertise of the Israeli Mossad intelligence service and the Jordanian GID service. Those agencies are the finest of their kind in the Middle East and the best placed to whip the Saudis into shape.
For a start, both services would educate the Saudi trainees that the best intelligence action is often the one not undertaken. In the case of a target like Khashoggi, they would have told the Saudis to ignore him or otherwise attempt to delegitimize him without using force. The concern here would come partly from a moral baseline, but also from the recognition that overreacting can cause far more harm than good.
As in this case, while the tactical method of the Khashoggi operation was very simple: trap him on safe ground (the consulate) and then kill him, it was toxic in both the moral and strategic conception. After all, it was inevitable that once the video footage of Khashoggi walking into the consulate leaked, it would be near impossible for the Saudi government to retain plausible deniability. It was also the height of idiocy for the Saudis to believe that Turkey's capable MiT intelligence service wouldn't have bugged the consulate or paid very close attention to the presence of Saudi intelligence officers on their soil.
But let's just say that it wasn't an innocent journalist but an al Qaeda or Iranian Revolutionary Guard terrorist that the Saudis wanted to get rid off. What counsel would their trainers impart in that case?
Well, I suspect they would educate the Saudis to the second rule of intelligence operations: keep things as simple as possible (the first rule being don't get caught unless you want to be). To that end, the Jordanians would attempt to infiltrate the target's inner circle by putting an agent or officer in his midst. The GID are already exceptional at this, and the Islamic State's decimation is at least part proof of it.
Of course, in many cases intelligence operations are necessarily complex so that the operation can remain undetected in means or outcome. In turn, the rule is not to avoid necessary complexity but rather to avoid the excited impulse of unnecessary complexity. The Jordanians and Israelis would suggest something simple to kill a single, high-profile terrorist -- a hit and run car crash, or a staged accident, or a robbery gone wrong, or a simple bullet or bomb to the head.
Where the target is especially sensitive in location or persona, the Israelis might suggest some kind of heart attack in a hotel room. That said, they would also suggest learning from their own embarrassment in 2010, when Israeli intelligence officers were identified on CCTV videos changing disguises without much apparent regard for being caught. They would also caution against the sloppy, risk-heavy tradecraft of Russia's marauding GRU service.
Regardless, the most important Israeli-Jordanian lesson would be the most basic: ensure first that the action is necessary, insulated from blowback, well-planned, and kept in the shadows.