Where do I start to optimize this SQL Query? - performance

Question

I have this sql query delivered from a customer which we need to performance optimize.
Is there anyone that can point me in the right direction to where to start looking for optimizing the following query?
The query on my local machine takes about 6-7 seconds, but on the users it´s about 30 seconds, It executes on a mssql 2008r2
Thanks!
var query = #"
DECLARE #SearchString nvarchar(250)
set #SearchString = '1811820001'
;with BaseSelectorCTE (ID) as
(
SELECT ID FROM BaseCases b
where
b.CPR like #SearchString
OR (b.FirstName + ' ' + b.LastName) like #SearchString
OR b.CustomerInfo_InstitutionName like #SearchString
UNION
Select ID from FlexjobCase
where Kommune like #SearchString
UNION
Select ID from DisabledAssistantCase
where Kommune like #SearchString
UNION
Select ID from AdultStudentCase
where Kommune like #SearchString
UNION
Select ID from DiseaseCase
where Kommune like #SearchString
UNION
Select ID from MaternityCase
where Kommune like #SearchString
UNION
Select ID from MiscellaneousCase
where Kommune like #SearchString
UNION
Select ID from WageSubsidyCase
where Kommune like #SearchString
UNION
Select w.ID from WageSubsidyCase w inner join JobCenters j on
w.JobcenterID = j.ID
where
j.Name like #SearchString
UNION
Select a.ID from AdultStudentCase a inner join JobCenters j on
a.JobcenterID = j.ID
where
j.Name like #SearchString
)
--
-- Select BaseCases mapped to result type
--
,ResultSelectorCTE AS
(
select
bc.Id as CaseID,
bc.ChildCaseName,
bc.CPR,
bc.FirstName,
bc.LastName,
bc.CustomerInfo_CustomerInfoID as CustomerInfoID,
bc.CustomerInfo_InstitutionName as InstitutionName,
bc.CaseDeadline,
bc.StatusID,
cs.Name as [StatusName],
cs.Owner as [StatusOwner],
bc.MetaData_Updated as [LastChange],
bc.LastActionDay,
,CASE bc.StatusID WHEN 9 THEN 1 ELSE 0 END as SidstePeriodeSoegt
from BaseCases bc
inner join CaseStatus cs ON
bc.StatusID = cs.ID
inner join BaseSelectorCTE bsCTE ON
bc.ID = bsCTE.ID
)
select * from (Select *, ROW_NUMBER() Over(Order By ##version , CASE WHEN StatusID = 9 then 2 ELSE 1 END, CaseDeadline ASC,
SidstePeriodeSoegt)
As rownum from ResultSelectorCTE where 1=1 AND StatusOwner <> 2 AND StatusOwner <> 3
AND SUBSTRING(CPR, 0, 3) BETWEEN 26-08-2014 AND 26-08-2015) As Result
where rownum Between ((1 - 1) * 100 + 1) AND (1 * 100);

Answer 1

Yes, the query execution plan:
The SQL Server Database Engine can display how it navigates tables and uses indexes to access or process the data for a query or other DML statement, such as an update. This is a display of an execution plan. To analyze a slow-running query, it is useful to examine the query execution plan to determine what is causing the problem.

Answer 2

Without knowing anything, start by losing the wildcards (*) sign. It's bad almost always as you are just saying, send everything and forgetting to actually review it.
Then, format your code correctly, CTE's are great, simplifies code, but it beats the purpose if your selects look like spaghetti, this has nothing to do with performance though.
Also, I had many times when UNION ALL outperformed UNION and I din't really think if duplicates were a problem or not, so you might want to look into that.
You didn't say if you are running it from Management Studio, are you on a local or remote server, how do the CTE's perform individually, etc. Context is king on this.
Hope this helps.