I've spent a lot of time listening to different reverbs and reading about the characteristics of each, and let me say it's a subject with a lot of opinion and taste. Fortunately, there are some universal things. Based on your screenshot, here's what each plug-in parameter does:
Dry Mix: How much of the unaffected (Non-reverbed) signal to blend into the output of the plug-in.
Wet Mix: How much of the affected (Reverbed) signal to blend into the output of the plug-in.
Link: I'm assuming this links the Dry/Wet Mix values.
Bypass: Turns the plug-in on and off. (I'm sure you knew this already)
Decay (S): This is how long it takes for the reverb to decay, or stop sounding, in seconds. This is called the RT60 factor. In technical terms, this is how long it takes (in seconds) for the reverb to reach -60 db.
Sparse/Dense/No Echo: This affects the reflections of the reverb. In a very large room, there's a long reverb time with sparse echoes. In a smaller room, there's a short reverb time with dense echoes. No echo bypasses this.
LP Filter: LP stands for Low-Pass, and you can think of it as a gate that only lets frequencies below the value be heard. This lets you sculpt the timbre of the reverb from the high frequencies down.
HP Filter: HP stands for High-Pass, and you can think of it as a gate that only lets frequencies above the value be heard. This lets you sculpt the timbre of the reverb more, and it starts from the low frequencies and moves up.
Active: This lets you turn off each filter.
My Suggestions on Setting Reverb
Get the time of the reverb first. Mix 100% of the wet signal in so you get an idea of what the reverb sounds like.
Once you like the time of the reverb, roll the wet/dry signals to taste. Think about what you're trying to do with the reverb and how much you REALLY need. Reverb is best in small amounts, as we tend to add a lot of reverb to projects.
Add the reflections (echoes). You may find you like some or none at all. Since you're new to this, you may want to do this step before adjusting the wet/dry signals.
Use the filters to get the reverb tone you want. You can make it bright, dark, warm, etc. Adjectives are pretty arbitrary - just picture what you want and move the filters to do it.
Keep in mind that there are an incredibly wide variety of reverb options - some costing thousands of dollars. The stock reverb plug-ins included with most programs (Especially Sonar) usually aren't great. However, that doesn't mean you can't make them work - it just takes skill and an understanding of what you want to do with it. Be patient and you'll get there. If you have any further questions, such as how EQ works with reverb, please feel free to ask.