You only need to seal seams that are exposed to water. Look for them in the floor, fly, and walls.
Don't bother sealing seams in the tents cloth roof. Roof fabric is water permeable so that air can circulate.
Several thin layer of sealant will work better than one thick layer. Thin layers also last longer.
Spread the rain fly out flat for sealing.
Seal reinforcements carefully. You may want to apply two coats on reinforcement seams.
Let the sealant dry for an hour or so. Do NOT put the tent away if the sealant is still wet. A ground sheet protects the floor and adds an extra layer of waterproofing. You can cut your own ground sheets. A ground sheet should be slightly smaller than the tent floor so the tent will completely cover it. If the ground cloth sticks out, it will funnel water under the tent.You can use newspaper to form a layer under your tent and this will also help to insulate the floor.

Tenting Tips
Picking A Campsite: Avoid low spots that collect water. Don't set your tent up under dead trees or branches that might fall. Once you've picked a site, clear the ground of sharp objects, small stones or branches.
Check the ground at established campsites for cinders or crushed stone. These improvements control erosion, but they can damage a tents floor quickly. In this case, a ground sheet may be essential, or small pinholes may develop in the tent floor.
Stake your tent down: ALL tents need to be staked to keep them from blowing away. Securing the tent by placing heavy objects inside is not adequate. The pegs packed with your tent work well in most conditions, but certain situations call for special pegs.
Sand: Long, broad pegs with plenty of surface area are ideal for use in loose, sandy, soil.
Hard, Rocky, or Frozen Soil: Spring steel pegs work well in these conditions. In extremely hard ground, use a ½" steel rod to make a starter hole. Store steel stakes separately. If you store steel stakes with your tent, the sharp edges may cut the fabric. Steel pegs can also leave rust stains which might damage your tent.
Snow: Use "dead man" anchors: bury objects (branches, aluminum pie plates, tent bags or stuff sacks filled with snow) that have a great deal of surface area. Tents can also be tied to snow shoes, skis, or ski poles which are stuck in the snow.
In severe weather - tie extra ropes directly to the tent frame at a crossing or junction point.
Limit ultraviolet(UV) exposure: Ultraviolet light is the invisible part of sunlight that causes sunburn. In a similar way, UV damages tent fabric over time. First, the tent's colours fade. As UV exposure accumulates, the fabric fibers are gradually destroyed. The fabric finally disintegrates.
You can prolong your tent's life by limiting its exposure to UV. Set your tent up late in the day. Pitching your tent in a shady spot will also help.
Don't keep food in your tent: Cooking and food odours attract wild animals. A hungry animal searching for food will chew or claw through the fabric, damaging the tent beyond repair.
Condensation: Through perspiration and breathing, an adult gives off about a half litre of water overnight. When you stay in a tent, this water vapour is trapped. If it cannot escape, water vapour reappears as condensation. Your tent's permeable roof reduces condensation, but can't eliminate it. Condensation is most obvious the morning after a cool night. You usually find condensation on coated fabric inside the tent. It can also form under sleeping bags, and objects that press the floor against the cool earth.
To reduce condensation, leave your windows partly open at night. Cross ventilation lets excess moisture escape, reducing condensation. Ventilation becomes more important in very humid or extremely cold conditions when your tent's permeable roof is less effective.
Zippers: Never force a jammed zipper. Instead, carefully remove any trapped material. If a zipper separates, gently pull the slider until the zipper is all the way open. Try to close the zipper again. The zipper may have repaired itself. Sand or grit can erode a zipper until it fails to close. If you use your tent in sandy soil, clean zippers frequently by flushing them with fresh water.
House keeping: Sweep out your tent daily to protect the floor. Since stones stuck in shoe treads can damage the floor, try not to wear boots or sneakers inside your tent.
Avoid contaminants: Some substances can damage your tent, including insect repellents, fruit juices, acid from leaky flashlight batteries, stove fuel, and hair spray. Keep all of these items away from your tent.
WARNING: Do NOT operate any device which burns fuel inside this tent. Combustion consumes oxygen, and can produce dangerous levels of carbon monoxide which could lead to serious injury or death.
Storage: Three words sum up proper storage: KEEP IT DRY. This prevents several problems.
Mildew: If you store a tent while it's wet, mildew will form. In addition to the odour, mildew damages the tent's waterproof coating, causing leaks. Sticky Coating. Leaving a wet tent inside its bag may ruin the coating. Over time a process called hydrolysis may soften coating, making it sticky. Sticky coating can peel off, letting water in.
Colour Transfer: Due to the nature of tent fabrics, colour can transfer from darker fabric to lighter fabric if two colours are in contact over time when damp. This does not effect tent performance.
Fold your tent loosely before storage.
Never store your tent directly on concrete. The chemicals in concrete will damage tent fabric.
Keep tents away from mice (they nest in tents).
Store your tent away from heat.

Comfortable Camping
You can soften the ground with foam camp mats and/or self-inflating camp mats.
Pocket size gas stoves and lights are efficient and reliaable. Battery operated lamps let you read inside your tent.