All the info below is good and informed, and describes the way things are usually done. I'd like to mention three items that are NOT part of standard practice, two of which are ESSENTIAL to a good result and one VERY valuable:

1. ESSENTIAL: What is the value that the sponsor(s)/investor(s) expect the project to generate, and what aspects of the deliverables/scope will have the most impact? (Without this, how do you plan scope?)

2. ESSENTIAL: What is the value/cost of time to the sponsor(s)/investor(s) for each unit earlier or later than the target date? (Without this, how do you finalize scope, schedule, resources, budget(s), fees, contractual incentives?)

A contract which does NOT take account of the above (like nearly all of them!) will almost certainly cause distortions and lead to inefficient project performance and very likely moral hazard through the principal-agent problem.

3. VALUABLE: The value breakdown structure (VBS): Which deliverables/activities are mandatory and which are optional? And for the optional ones, what is the approximate value-added of each? (Projects are being completed every day that include deliverables/work that have NEGATIVE value-added, i.e., their value-added is less than their TRUE COST, where true cost = drag cost + resource costs.)

For step-by-step details on detailed planning and optimizing of a project as an investment, I recommend the second edition of my book Total Project Control: A Practitioner's Guide to Managing Projects as Investments.

Fraternally in project management,

Steve the Bajan

glad we could help 

There are a lot of free resources available under a 'Cereative Commons License' for you to use and adapt at: https://mosaicprojects.com.au/PMKI-SCH.php

Good proceedures are simple and short - don't prescribe too much until the organisations culture matures and you know what is needed. 

updated part 

1. copy the previous schedule

2. apply progrees indicating any actual start dates and remianining durations (this is for activities started but not finished)

3. apply progress indicating actual start date and actual finish date (this is for activites started and finished)

4. apply progress actual finish date (this is for activites started previously and are now finished)

5. change the data date run the forward and backward pass (F9) and look at the progress today pre change orders

6. Incorporate ALL change orderes issued during this update period.

7. Progress any change orders this period 

8. re-cacluate the schedule (F9) this is progress post change orders 

9. Look at the output file from the calculations and correctly any out of sequence progress

10. re-cacluate the schedule (F9) 

11. Create a new activity code called now-critical and give it a code value of CP

12. filter for the last activity in the schedule

13. look at the predcessor window make sure that critical and driving are there

14. click on the activity in the precessor window that has BOTH criticla and driving boxes filled in and select GOTO

15. Keep doing this until you get ack to the activity that i son the data date

16. Select all activies that you just went GOTO and right click and select assign and assign them to the code now-critical code with the CP vlalue. This is your critical path. Now you can filter for where now-critical equals CP.

17. Look over the schedule look for very long durations (could be a type O) make sure the critical path make sense

18. look for any actual dates greater than the data date (could be a type O wrong year)

19. Create the monthy schedule narrative (but thats a whole different story)

next month do it all over again

as Santosh stated there are some existing standards out there for scheduling but you need to 1st focus on how your company operates. This depands alot on the type of bussiness and business sector that your compay is in. It appears that your current business is railway tracks. 

1st find out how a project originiates ? 

2nd who originiates it  ? someone maybe a manager or someone says lets bid on this project (if it is a public sector bid project)

3rd and estimating team looks at the scope and begins to put together an estimate on how much money it will take to do this project within given scope and within the allotted time frame. From this estmate is where your planning process begins. You should be able to get manhours from the estimators. These manhours are then used to determine you durations. The estimators will also be getting durations for long lead time items. 

4th now you have to plan (if not identified) how you want to approach your work this is where you begin to delevope thw WBS (work breakdown structure) mybe like the following 

By Phase

    then by Geographical area

         then by direction (north to south or south to north) or (east to west or west to east)

              then the typical sequence what comes 1st what comes second (the logic) 

5th After the wbs define your calendars (how many hours per days and how nay days per week) also since this is outside rail work you should consider adding non work dasy each month for anticipated adverse weather base don teh geographical location of the project. 

6th define any coding that you want to use in the schedule this will be used to group and sort and filter activiites 

7th apply the durations and your activities (it this point you can calculate the scheduel) 

8th  apply the codes to created to all of the activiites 

9th add a resource and assign the resources to each activity 

10th revise the manhours and cost for each activity in teh schedule (the defult will multiply the Max Uiits/ time (8) by the durations to give your defaul manhours or UNITS. Put in the appropriate costs for each activity.

11th create the histogram to see number of men needed. 

12th create the S curve to see the anticipated cash flow curve.

13th chekc teh schedule against industry standards such as the DCMA 14 point schedue assessment (even though you are in the UK this does not change the required quality of the schedule).

THATS THE PLANNING PART 

now you need a whole other process of the updaitng part which of course I have