With your XS/1000D, you have no built-in capability to trigger a remote flash in wireless eTTL. The XXXXD range of Canon dSLRs have never had this capability. The XXXD dRebels only have it with the T3i/600D and later models.
Wireless eTTL
To use Canon's proprietary "wireless eTTL" triggering, you'd have to use a master unit on the hotshoe: a 90EX, ST-E2, 550EX, 580EX, 580EXII, or 600EX-RT, if you want to stick with Canon gear. There are also master units from Metz, Nissin, and Yongnuo, but this path is probably still more expensive than you'd want to take just to see if you like it. However, Canon's optical "wireless eTTL" system does have the advantages of giving you eTTL and high-speed sync wirelessly, and a way of remotely changing settings on the off-camera flash.
But, of course, that's not the only way you can trip a remote flash.
Radio Triggers
Cheap radio triggers are probably the most common way used to trip remote lights, because these days everyone reads the Strobist. :) Cheaper ones will be manual-only (i.e., can only communicate the sync/fire signal, and nothing else) and typically don't offer eTTL. A few may offer HSS, or remote power control but are likely to be more expensive. A transmitter unit is placed on the camera hotshoe to send the sync signal, and a receiver is connected to the flash (either on its foot or through a sync connection with a cable—if the flash has a sync connection; the 430EX doesn't) and the signal is relayed over radio from the camera to the flash. This system has the advantages of being robust and low cost, but the functionality is minimal.
There are also radio triggers that can communicate the full hotshoe protocol with high cost and reputation (such as Canon's -RT system, RadioPoppers, PocketWizard TTL) and less-high cost and reputation (Pixel Kings, Phottix Odins, Yongnuo YN-622); but you do need to scale the cost per unit to the number of lights you plan to use. I.e., a $100 trigger doesn't sound super-expensive, until you realize you want to use four lights, so you'll need five of them.
Dumb Optical Triggers
There's another kind of optical trigger that isn't eTTL/HSS-savvy, but can fire the flash. Many third-party flashes and studio strobes come with these built-in (why Canon's EX speedlights don't, we haven't a clue). A Yongnuo YN-660 or Lumopro LP-1x0, for example, have slave modes that fire the flash when another flash burst is sensed. This can be set off by a simple point-and-shoot flash burst, as well as other studio strobes. You can also add one onto a flash (although only the green-based Sonia slaves seem to have a reputation for working with Canon EX flashes reliably), but they typically require some kind of sync connector. If you get a 430EX, you'd have to add a hotshoe-to-sync port adapter as well, at which point a cheap radio trigger might cost the same or less.
Optical slaves have the weakness of requiring line-of-sight (the sensor has to "see" the mastering light pulse), and range may be reduced in low-contrast conditions (i.e., shooting outside in bright sunlight where the sun can overpower the signal). Used indoors with lots of bounce surfaces, optical systems usually work very well. Outside in bright sunlight is another story. And this goes both for "dumb" and "smart" systems. Light-based is still light-based.
Sync Cables
You can also go wired, rather than wireless if you really want a good robust low-cost backup triggering system. And again, there are manual-only cords and TTL cords. The TTL cables will have hotshoe-to-hotshoe connectors; the manual-only cords basically have 2-signal connectors that can communicate the sync signal and ground. PC (Prontor-Compur), 3.5mm (aka 1/8") miniplug, 6.35mm (aka 1/4") phone connector, and household connectors are all used on manual-only sync cables. The problem is that a manual cable with your camera/flash combination would require that you add sync ports to your camera and your flash, so you'd also have to price in hotshoe adapters, at which point manual radio triggers might cost the same or less.
