On a gutter the bulbs point out. On shingles the same clip points them up. A roofline that changes surface changes orientation.

Decide the bulb orientation, then pick mounting to match it

Christmas Designers states it directly: all-in-one style clips align C7 and C9 bulbs horizontally with the tips pointing out when mounted on gutters, and vertically with the tips pointing up when mounted on shingles. Christmas Lights Etc describes the same behavior, noting that on a gutter you slide the clip over the lip so the flat part of the tab sits against the backside of the gutter. So the orientation is a consequence of the surface unless you make it a decision. Walk the roofline first, note where it changes surface, and settle on one look for the whole run. Then choose clips and mounting positions that deliver it, rather than clipping whatever is easiest at each point and discovering the inconsistency from the driveway.

Staples cost you the ability to fix it, not just the holes

The damage argument is well known and true. The argument that actually changes behavior is the one Christmas Lights Etc make second: staples and nails leave no room for adjustment once the lights are in place. Holiday lighting is a job where the first attempt is rarely the best one, because sag, spacing and straightness only become visible from the ground once the run is up. With clips you can slide a socket along, add one at a droop, or lift a section that reads low. With staples you either live with it or make more holes. That is worth more than the damage argument to anybody who has stood in the street squinting at their own roofline.

Match the clip to the surface, and know which surfaces defeat which clips

There is a clip type for each surface and using the wrong one produces specific symptoms: C9 bulbs sagging, mini lights getting pinched and cracked. Gutter clips hook over the lip of a standard gutter. Shingle tabs slide under the shingle edge, with better ones offering a fold-over tab and a dual leg for grip. All-in-one and omni clips do both, which is why they suit transitioning rooflines. A gutter guard or leaf screen needs the clip turned so the curved hook faces up and snapped into the screen, which is the opposite orientation from the same clip on a gutter lip. Magnetic clips are fast and leave no residue on metal garage doors, fascia and beams. And the trap worth memorizing, stated plainly by a supplier: brick is not ferrous, so magnetic clips will not work on it. For brick and stone the answers are adhesive-backed clips or traditional brick clips set into the mortar lines.

On sandwich-style clips, the clip goes on before the bulb

A sequencing detail that is annoying to discover halfway through. Christmas Designers describes their Tuff Clip as being placed on the base of a C7 or C9 light line before the bulb is screwed into the socket, so the bulb sandwiches the clip in place, which is what stops it coming off and what makes removal quick at the end of the season. That is an excellent design and it only works in that order. If you bulb an entire socket line and then reach for that clip style, you are unscrewing every bulb to fit them. Decide the clip before you bulb the line, which is another argument for doing the whole assembly on the ground.

Check the clip works with the kind of lights you actually have

Clip compatibility is not universal and the distinction that catches people is between empty socket light line and factory stringer sets. Christmas Designers notes that the Original Shingle Tab works with C7 and C9 empty socket light line and retrofit bulbs but does not work with stringer-style light sets. If you are chaining factory sets rather than building your own runs, that rules out some of the best clips in the trade. Check which family your lights belong to before ordering a thousand clips, and check the bulb sizes too, since clips are made for specific ranges and a clip that does not hold the bulb is worse than no clip.

Spacing is a design decision, not a default

Worth knowing because it is the difference between a display that looks bought and one that looks designed. Twelve inch socket spacing on C9 is described as the classic roofline look. Closer spacing reads brighter and more premium, and wider spacing reads more vintage. None of those is wrong, but the choice should be deliberate and consistent, because mixed spacing along one roofline is another one of those things that looks like carelessness from the street. If you are building your own socket line you are choosing this directly; if you are using factory sets, the spacing came with the product and your job is to keep runs of the same product together.

Wind takes corners and peaks first

The practical advice is consistent across suppliers and it is about clip density rather than clip strength. Clip every socket rather than every second or third one, do not overstretch the line between clips, and add extra clips at corners and peaks. Those are the points where the line changes direction, where the wind loads are highest, and where a single failure drops a whole span. Overstretching is the subtler mistake, because a line pulled tight to make it look straight has no slack to absorb movement and transfers every gust straight into the clips at each end.

Leave the clips on, and keep them out of the sun

Clips are reusable and the way to make that true is to stop treating them as loose hardware. Leave them attached to the socket lines when you take a display down, coil each run neatly, and label it by location, something like front gable, C9 warm white, forty-two sockets. Next season becomes a reinstall rather than a rebuild. Store indoors and specifically away from UV exposure, because these are plastic parts and sunlight is what makes them brittle, and a brittle clip snaps on the ladder rather than in the box. Keep the different styles in separate labeled bags, since sorting mixed clips in December is the exact task nobody wants.