There is stealth in space. All smugglers know this. It's inside your ship for the most part. Smugglers are very similar to pirates or the total opposite depending on who you ask. An old joke goes there was a smuggler who switched to piracy thereby raising the average IQ of both groups.
In terms of economics pirates risk the well being of their ships and crew to gain loot which is a 100% profit (minus a little liquid hydrogen for the lasers and drives assuming the target doesn't fight back). Smugglers are trying to beat out government duties, tariffs and taxes and running a much smaller risk of their freedom and ship.
Smuggling is fairly easy to grasp. You find a planet that imports and heavily taxes a commodity that is relatively cheap. You buy the commodity and deliver it to that planet in a way that avoids the tax man. Or better yet find a commodity that is highly sought after on one world but illegal. Buy it where it is legal, sneak it to where it is illegal and set blasters to gouge.There are a number of ways to do this.
The simplest way is to find or create a hiding place in your ship. Make sure it's a very good place and don't even bother stashing it behind the radiation shields. Customs has robots, drones or day laborers and make them look there first. You only have one shadow shield to look behind but there are way more corridors to check and customs has a lot of ships to check if you're doing it right.
Removable door, floor, and ceiling panels are much better and honor tradition. Optionally you can put your illicit cargo (if it's small enough) someplace the customs inspectors wouldn't want to go. So you might hide your load of hot jewels in the flooring of the crates holding your cargo of venomous rock pincers for Durella 3. The would be smuggler is encouraged to find the most dangerous, toxic and unpleasant materials to haul that he can. Check the dumpsters behind fast food chains. Hiding packages in your ship's recycling system is a fine dodge as well.
If you're dealing with high tech customs inspectors then they may have all manner of sensors to look through walls. An extra laver of deception will be necessary in this case. Merely blocking the sensors will raise all kinds of eyebrows. The trick then is to disguise your contraband as something innocuous. Stick those auto rifles in with the farming equipment. Hide the psi boosters in bottles of aspirin. For those who have a crew ready to go the extra parsec ... customs doesn't usually do internals scans of human beings.
Hiding items in plain sight is often possible. One gentleman scoundrel would have a chilled pitcher of martinis ready when the customs inspectors came aboard and offer them a libation. The inspectors never accepted and found anything until one old commander on his last day before retiring agreed to a drink. After the inspector nearly choked to death on the stolen moon crystals hidden in the ice the smuggler lost his captain's license, ship and was sentenced to 20 years for poisoning a public official.
Disguising one thing as another is another common dodge. The pseudoraptor you're transporting might be a member of an endangered subspecies protected by law but the inspector won't want to get close enough to see past the dye job.
There is also the old shell game. A smuggler took on a cargo of on a desert world with no refueling facilities. He made for the local gas giant to refuel his Scout Courier. The local authorities learned of his activities and when a Navy patrol ship jumped into the system called in the violation. The patrol ship chased the smuggler all the way to the gas giant and got within shooting range just as it dipped into the clouds. The patrol ship shut down it's power, and lay silent above one of the poles where it could observe and wait for the smuggler who was refueling via an equatorial orbit. That was when three Scout ships emerged and headed in different directions. The patrol ship might have caught one but not all three. Two got away and the one that did get boarded had nothing. They claimed communications system damage kept them from receiving the patrol ship's hails and transponder id. It was probably caused by lightning storms while refueling.
The hard part of smuggling involves dodging the customs inspectors entirely. Maybe you have the big score taking up most of your hold. It is possible to land unnoticed at many times though these sort of stunts are usually confined to starport classes of A or D. We're not counting class E or X. Anyone can land anytime at those worlds.
Type A 'ports simply have too much traffic to stop every ship. A bribe in the proper circles or an anonymous tip to another ship and you could slip in with the law abiding citizens. A class D starport will not have a huge amount of traffic but it will also not have extensive sensors nd a savvy navigator could chart a course away from prying eyes.
Smuggling can also be from point to point on a single world. A low tech and balkanized world might have battalions guarding its border but a minor space presence. Moving goods from one nation to another can be as lucrative as between planets and much quicker. Just get out when one side or another gets starship missiles to load in their launchers (you aren't the only smuggler you know.)
Space tactics also involve stealth via distraction. One group of smugglers hit on the Jump Blind Tactic. Ship A launches from Planet Backwater. It heads for a point in space where Ship B carrying illicit cargo emerges from jump space (timing is very important obviously.) When Ship B emerges Ship A vents a load of plasma from its reactor (and will later claim engine malfunction). Ship B has its emergence hidden by the hot plasma. The ships dock and the illicit cargo is transferred to Ship A. Ship A makes a show of limping back to port as Ship B jumps out of system (or uses various kinds of flares to mimic its jump signature) and heads to port looking innocent and freshly emerged from jump. When Ship A gets to port it peddles the illicit cargo having been through customs inspection already on its way out. One smuggler operating out of a type D port made a show of chronic drive trouble and limping back to port a couple times till the trouble was fixed. The port itself was kept quite busy by the couple of extra ships that showed up that month.
Some smugglers have used modified missiles to deliver contraband, launching the missiles on a ballistic to their destination. Others have launched missiles that flew ahead inert until the ship rendezvoused with a customs inspector and were then picked up. Missiles can be chilled way down till they have almost no heat signature.
One rule of smuggling is kept by almost everyone: no phony distress signals. Smuggling is a nonviolent crime (unless you serve deadly toxic gemstones to an inspector.) A distress call can pull search and rescue ships as well as navy patrols away from a real emergency. That can result in death and there's a world of difference between losing your captaincy and ship and being sentenced to death or life imprisonment. After all, who would smuggle you out then?