A fresh grid has forty or fifty empty cells. Looking at all of them at once gets you nowhere. It pays to have an order: look first for what you can see quickly, and only then for what takes work.
The order
Last numbers. A row, column or box with a single empty cell solves itself: it is the last number.
Scan, from the most frequent number to the least. This is scanning, which finds hidden singles. First in the boxes, then in the rows and columns.
Write the notes when no more numbers can be found, and look for cells with a single candidate: the naked singles. See pencil marks.
The Medium techniques: pointing, claiming, naked pair, hidden pair. They don't place numbers: they remove candidates from the notes. Every candidate removed may reveal a single.
The rule that matters most is also the one most often forgotten: after every number, go back to the start. A new number may complete a unit or leave a box with a single place for another number. Looking for pairs with a last number in view is doing the hard thing before the easy one.
Start with the number that appears most
A number that is already in the grid seven times only has two places left to fill. Its seven rows and seven columns cross out almost everything. That is where you start.
At the start of this puzzle, the 9 appears seven times; no other number appears more than four. Two are missing: one in box 1, the other in box 8.
In box 1, the 9s in rows 2 and 3 cross out the bottom two rows of the box. Of the seven empty cells, three are left.
The 9s in columns 1 and 2, further down, cross out two of the three that were left.
The cell in row 1, column 3 is left: that is where the 9 of box 1 goes. The same happens in box 8. The 9 is complete before you have looked at any other number.
A number that appears five or six times usually gives you something too. One that appears once or twice hardly ever does at first; leave it until the grid is fuller.
When you get stuck
Change unit. If you only scan the boxes, you forget the rows and the columns. Some hidden singles only show up there.
Check the notes. A missing note makes a cell look as if it has fewer options than it does; an extra one hides a naked single. Redoing the notes of a unit costs little.
Don't guess. Every Urso Pardo puzzle can be solved by logic alone. Placing a number «to see if it works» can lead to a wrong grid. The mistake only becomes obvious much later, when it is hard to tell where it started.
Ask for a hint. The game's hint follows this same order: it always names the simplest technique that makes progress, then where it is, and only at the end the whole step. If there is a wrong number in the grid, or notes missing the right number, it says so first. It counts as help, from the first step.
Your turn
Positions from puzzles halfway through. Place a number, any one that can be found with the Easy techniques: last number, hidden single or naked single.