Flight Following best practice for student pilot

@Dave's answer is mostly somewhat correct, but not entirely.

I am an air traffic controller and this is my take on your questions. Also remember that you have a CFI, and you absolutely should be discussing this plan with them. They will have more specific local knowledge than I do; I'm making some (very educated) assumptions as to how the ATC side of things work in this area.

Terminology

• VFR flight plans are "opened" and "closed" with Flight Service. VFR flight following (radar service) is "requested" and "terminated" with ATC.
• DO NOT say the leading "Kilo" when talking about airports. Four-letter codes are ICAO airport codes, and in the Lower 48 the ICAO code will always be composed by taking the three-letter FAA Location ID and adding a Kilo on the front. The leading Kilo is 100% useless and you should never say it when talking to ATC. Use the FAA LID itself.
• For that matter, just say "Sailsbury," "Millville," and "Bay Bridge." These are all short flights and the controllers you're talking to will all be familiar with these airports.
• Like I said in my comment, KW29 is not a valid ICAO code, nor is it a valid FAA LID. It does not refer to any airport anywhere in the world. W29, which is an FAA LID, is the one and only code referring to Bay Bridge Airport in any identifier system. KW29 is the National Weather Service identifier for the weather station that is located at Bay Bridge Airport.

Requesting flight following

You don't need to wait until you reach cruising altitude to make your request with ATC; call when you can, tell them your current altitude, and tell them your requested altitude.

On departing W29, request flight following with Potomac Approach. You're still within their airspace, but keep your request brief and be prepared for an almost-immediate frequency change to another Potomac frequency, if not a frequency change straight to Patuxent Approach. If it takes you a while to get a word in with Potomac, you might call Patuxent directly once you pass ESN; the sectional has a little box telling you to call 127.95.

SBY has a tower; you should make your request for flight following when you are on the ground, going zero knots, with the Salisbury Ground controller (unless the ATIS tells you that all positions are combined at Salisbury Tower). Maybe they can coordinate that request for you; maybe they can't, and they'll tell you to call Patuxent after departure. You don't know until you ask.

There's no tower at MIV, so again you'll have to call airborne; whether that's Atlantic City Approach, Dover Approach, or maybe even Philly Approach will depend on exactly where you are when you call. I would lean toward Dover just because you're headed toward their airspace—rather than Atlantic City because you're headed away from them—but your CFI probably has better info.

Staying on flight following

Yes, stay with the controller until they terminate you. Do not change frequencies without asking the controller first. If you need to change frequencies temporarily in order to get the weather/ATIS, say that; if you're within ten miles of the airport and you request a frequency change, the controller will know that means you want to be on CTAF and they will give the "radar service terminated" spiel.

Unless otherwise restricted, you don't have to ask the controller for an altitude change when you're VFR. However, you will be flying in pretty congested airspace and I would bet they'd appreciate a heads-up if you're going to change your cruising altitude. Don't bother advising them that you're starting your final descent to pattern altitude; we expect you to start down as you approach your destination.

Nearing destinations

DO NOT report the field in sight, unless the controller specifically asks. It is never necessary for a VFR aircraft to report the field in sight, but some controllers want you to say it; they are working harder than they need to. Say what you actually mean! If you want permission to change frequencies, say "N345 request frequency change."

SBY has a tower. It may be that radar services will be terminated and you'll be instructed to squawk VFR before contacting them, or it may be that you'll be told to keep the squawk (or told nothing at all besides "Contact Salisbury Tower," which also means "don't change the squawk"). Depends on local procedures.

Expect radar services to be terminated when you get close to MIV and W29, yes.

Re-requesting FF

Are you planning on making a full-stop-taxi-back at each airport, or just doing touch-and-goes?

If you'll be doing FSTBs, make each flight following request separately, and only as far as the next destination. DO tell Salisbury Tower that you want a FSTB, so they don't try to direct you toward the FBO. Patuxent Approach probably doesn't care, though.

If you'll only be doing touch-and-goes, still request FF only as far as Salisbury when you're talking to Potomac Approach. Once you get handed off to Patuxent, or if you end up calling them directly, you can tell them that you plan on a touch-and-go at SBY and then continue to MIV. They can figure out what works best for them: Have you keep the same squawk code, or put you in on a different code to MIV.

This is a few questions wrapped into one so a few answers for ya:

1. Flight following is opened once airborne since you are leaving from an un-towered field, and requested to the destination, this holds through climbs and decent, do not close it on every flight portion, its likely to be the same controller anyway. When on FF you do not need to request altitude changes either (I hear this mistake often), you will simply get a grumbly controller respond with "Altitude at your discretion", unless you are flying in controlled airspace and were assigned an altitude for some reason, remember you can always deviate to remain VFR.
2. You generally should report field in sight and cancel your own FF if you are still in the system, this keeps anything from being a question and generally lightens the load on the controllers.
3. If you drop out with out canceling it it will effectively be terminated, they may try to hail you on the frequency so its good practice to pro-actively cancel
4. Yes, re-request after departure its a new flight to a new destination.

Cheers on your solo XC I did my first one to KSBY as well!